IRBIL, Iraq — Jet aircraft attacked Islamic State positions outside the town of Kalak, 25 miles northwest of Irbil, the capital of Iraq’s autonomous Kurdish region, a resident of Kalak told McClatchy early Friday.

The resident, reached by phone from Irbil, said she had seen the aircraft and had heard the explosions coming from behind Islamic State lines, which are slightly more than a mile away. The resident said because it was dark she could not see any markings on the aircraft.

Kurdish television reported that the bombers were American. There was no confirmation from U.S. officials in Washington.

The reported bombing came after a day of panic in the Kurdish capital following Islamic State militants’ seizure of four strategic towns on a key highway and their advance to positions just minutes from Irbil.

Hundreds of Kurdish peshmerga militiamen built earthen berms near Kalak on the highway that links Irbil with Mosul, the Iraqi city whose fall to Islamic State militants in early June touched off a sweep across northern and western Iraq that until Thursday had spared Kurdish areas.

But that quiet appeared to be over, with the Islamic State boldly saying in an Internet posting Thursday that it intended to capture Irbil, a city previously thought so secure that the United States two months ago chose it as one of two Iraqi cities safe enough to receive scores of staffers evacuated from the U.S. Embassy in Baghdad.

“The Americans keep saying they will help us,” said Rosg Nuri Shawess, a top Kurdish military commander who was overseeing the defensive preparations. “Well, if they plan to help they had better do it now.”

From Kalak, about 25 miles northwest of Irbil, the front line of the Islamic State, which everyone here refers to as “Daash,” an Arabic acronym, could be seen slightly more than a mile away.

“Daash is testing our defenses,” said Shawess, who is a member of the Iraqi government’s national security council, pointing to two towns that fell Thursday to the Islamic State, Qaraqosh and Bartella, that were visible in the distance. “And if we don’t show them we are strong here, then we have lost Irbil.”

U.S. officials were cagey throughout the day about what the United States planned to do to help fend off an Islamic State thrust at Irbil, where the U.S. also has recently expanded its CIA station and set up a Joint Operations Center to coordinate military activities with the Kurdish and Iraqi governments.

U.S. officials said specifically that the U.S. was considering dropping supplies to refugees trapped on a mountain near the Islamic State-controlled city of Sinjar.

The Kalak resident told McClatchy that her relatives near Sinjar had been told to stay away from the city and that many Sinjar residents were moving to leave the city.

But there were no specifics about military steps to counter the Islamists’ move toward Irbil. At the White House, spokesman Josh Earnest stuck closely to the administration’s months-old position that Iraq’s problems must be solved politically.

“There are no military solutions to the problems of Iraq,” he told reporters. He said the United States would move to protect American personnel but that American military action “would have to be closely tied to Iraqi political reforms.”

A sense of dread fell over the Kurdish capital as the magnitude of the threat became clear.

Western oil companies based in Irbil shut down operations and restricted their employees’ movements out of concerns for safety, while makeshift shelters popped up in public parks and churches in the Ain Kawa neighborhood to accommodate hundreds of people who had fled the newly occupied towns. There was a noticeable increase in the presence of the Kurdish peshmerga militia in the city, and there were reports that hundreds of residents flooded the airport in hopes of buying tickets to elsewhere.

A refugee camp at Kalak that only two days ago was filled with tens of thousands of refugees who had fled Mosul when it fell to the Islamic State was empty Thursday as the area became the new front line of a conflict that went from occasional clashes to a full-scale war between the Kurds and the Islamic State in less than a week.

Content to sit in Mosul and consolidate their grip over much of Iraq’s predominately Sunni Arab areas for six weeks, militants from the Islamic State first seized the city of Sinjar and key areas around Mosul Dam from Kurdish forces over the weekend. By Wednesday, the Kurds counterattacked in Sinjar, bolstered by thousands of fellow Kurdish fighters from Syria and Turkey. But the Islamic State responded with a range of attacks along the nearly 900-mile border separating the two sides, then seized the Mosul Dam and captured the Christian towns of Bartella and Qaraqosh on the way to Irbil.

The peshmerga appeared to be preparing to make a last stand at Kalak. Several hundred regulars in uniforms with well-maintained light weapons and heavy machine guns, backed by a few armored vehicles and a single Soviet-era T-55 tank, were digging in with earth movers along a string of desolate desert hills to prepare for what a top security official called a “very serious test.”

Shawess, the officer in charge of the forward lines, said his men were confident and well trained, a claim reinforced by the professional demeanor of his uniformed men. But the peshmerga will face Islamic State fighters armed with advanced U.S. weapons with just a handful of 12.7mm Soviet-era heavy machine guns and rocket-propelled grenades.

“We need better weapons and help,” Shawess said. “They tried to attack this morning but were just testing us.”

Shawess said those attacks recalled the first Islamic State moves in Mosul before that city fell to the Islamists June 9.

“These tests are critical,” added Shawess. “When they first attacked Mosul I don’t know if they planned to take it, but when there was no resistance they acted quickly. We have to show them here they can’t take Irbil.”

He was hardly exaggerating. The 25 miles from this new front line to the outskirts of Irbil – barely a 30-minute drive – remained virtually undefended beyond the occasional cluster of peshmerga fighters on hilltops and another single T-55 tank sitting in an intersection about halfway down the road.

The Kurds have a long, proud history of military prowess, and civilians and retired peshmerga were turning out in force to support their uniformed compatriots. But while they were enthusiastic in their traditional Kurdish clothing, they seemed far more interested in recounting the history of previous victories than in preparing for a soon-to-come onslaught. Their weapons were a motley assortment of family firearms, some modern, many antique. Some men, old and portly or young and untrained, manned a series of checkpoints closer to the capital, with an eye for Arabs driving cars with Mosul plates. Some merely stood around.

“I have come to defend my country,” said Yassin, 60, who wore traditional tribal clothes and carried a Russian-made Dragonov sniper rifle, missing its scope, rendering it basically useless except for close-quarter fighting. “All Kurds know how to fight.”

But despite the positive attitude, word from the various fronts around Kurdistan was grim.

The Mosul Dam had fallen to the Islamic State, U.S. and Kurdish officials confirmed. It is the largest such structure in Iraq and controls a major Iraqi watershed, amid fears that the Islamic State could unleash a torrent of water and inundate hundreds of square miles of Iraq.

The link between Irbil and the Iraqi city of Kirkuk to the south, which fell under Kurdish control when Iraqi soldiers fled in June, also appeared in danger, with reports that the Islamic State had taken at least partial control of Makhmour, a town that lies along the primary highway between the two cities.

Falah Bakir, the foreign minister for the Kurdistan Regional Government, said in an interview with CNN that the Kurds faced disaster and needed immediate assistance. “We are left alone in the front to fight the terrorists of ISIS,” he said, using an acronym for the Islamic State, which used to call itself the Islamic State of Iraq and Syria.

“I believe the United States has a moral responsibility to support us, because this is a fight against terrorism, and we have proven to be pro-democracy, pro-West and pro-secularism,” Bakir said.

“I now know that the towns of Qaraqosh, Tal Kayf, Bartella and Karamlesh have been emptied of their original population and are now under the control of the militants,” Joseph Thomas, the Chaldean archbishop of Kirkuk and Sulaimaniyah, told the Agence France Presse news agency. The fall of those villages represented the loss of the largest Christian communities in Iraq.

Kurdish officials repeatedly have claimed that the United States and the Iraqi government in Baghdad have refused to send military aid and that they have only Saddam Hussein-era weapons and limited ammunition to counter Islamic State forces that are armed with advanced American weaponry.

A statement attributed to the Islamic State posted Thursday on the Internet said that the Islamists would target Irbil as retaliation for Kurdish officials’ agreement earlier this week to coordinate operations against the Islamic State with the central government in Baghdad.

“We are pleased to announce to the Islamic nation a new liberation in Nineveh province, teaching the secular Kurds a lesson,” the statement said.

The United States has long been seen as the Kurdish region’s protector. After the first Gulf War ended in 1991, the U.S. imposed a no-fly zone over the region to prevent Saddam’s air force from attacking. The Kurdish zone became a rare outpost of economic development in an era when harsh trade restrictions were imposed on the rest of Iraq. After U.S. forces toppled Saddam in 2003, the region enjoyed enormous autonomy and was largely free of the sectarian warfare and chaos that plagued the rest of Iraq during the American occupation.