KANDAHAR, Afghanistan – Afghan security forces fought back against a fierce Taliban onslaught by about 800 militants in a key southern province Wednesday as clashes that have killed dozens of people, including at least 35 civilians, stretched into a fourth day.

The Taliban attacks targeting checkpoints and government buildings in Helmand province – which was touted as a showcase of a major U.S. military offensive to drive out the militants in 2009 – show the stark challenges facing government troops trying to defend the country against the resilient Islamic militants with diminishing help from the international community.

Afghanistan’s security situation has been complicated by a political crisis stemming from allegations of massive fraud in the recent election to replace President Hamid Karzai, the only leader the country has known since the Taliban regime was ousted nearly 13 years ago. Abdullah Abdullah, one of two candidates who competed a runoff vote on June 14, suspended his relations with the Independent Election Commission after he accused electoral officials of engineering extensive vote rigging, allegations they have denied.

His rival, Ashraf Ghani Ahmadzai, called on Abdullah to rejoin the process and demanded that the commission stick to the official timetable for releasing preliminary results next week.

“We believe that the only way forward is full adherence to the constitution, to the election law and to the regulations. We therefore are dismayed that our esteemed colleague Dr. Abdullah has withdrawn from the process. Our request to him is simple – join back to the process. Respect the will of the people,” Ahmadzai, a former finance minister and World Bank official, told supporters at a rally.

Afghan soldiers and police were applauded last year for largely holding their own against the Taliban, but the militants have stepped up their campaign of violence in a bid to undermine the Western-backed government. The relentless insurgency has raised concern that the departure of most foreign forces will lead to new instability in the war-weary country. The Obama administration has said it would leave some 10,000 American troops in the country if a much-delayed bilateral security pact is signed. That would also pave the way for thousands of forces from other NATO countries to remain.

NATO foreign ministers discussed Afghanistan’s future after the alliance’s combat mission ends in December in a meeting Wednesday in Brussels.

The alliance’s Secretary-General Anders Fogh Rasmussen said the goal was to launch a new mission called “Resolute Support” to train, advise and assist the Afghans at the start of next year.

“But it is the Afghans who must take the next step,” he said at a news conference. “The necessary security agreements must be signed soon. Otherwise, we will not be able to keep any troops in Afghanistan from next year.”

Karzai, who is constitutionally barred from seeking a third term, brokered the deal but then refused to sign it, saying he would leave the decision to his successor.

Both candidates have promised to sign the agreement soon after taking office. Final results are due on July 22, and Karzai has set Aug. 2 as the date of the inauguration of the new president.

Ahmadzai denied any involvement in fraud, saying his campaign team had itself registered 1,800 complaints of irregularities that needed to be investigated. He refused to offer specific forecasts but said his team’s analysis shows that votes for him had increased in each of Afghanistan’s 34 provinces.

The ongoing clashes in Helmand come as the Taliban have launched their so-called summer offensive, in which fighters take advantage of warmer weather and easier movement in the mountainous country to increase attacks, posing a major test of the capabilities of Afghan forces.

Taliban fighters began attacking police checkpoints in Helmand’s Sangin district on Sunday, forcing the government to send reinforcements to bolster the local security forces.

Afghan Defense Ministry spokesman Gen. Mohammad Zahir Azimi said Wednesday that the clashes had spread to three other districts, Kajaki, Musa Qala and Nowzad.

The Taliban push to reassert control in former strongholds is particularly significant because Helmand province was the site of a major U.S. military offensive in 2009 to drive the militants from the area.

The U.S.-led coalition said Wednesday that it was providing support to the Afghan national security forces in the area over the past 72 hours, including helicopter escorts for medical evacuations, intelligence, surveillance and reconnaissance assets and close air support. “All checkpoints in Helmand are currently under ANSF control and this remains an ANSF-led operation,” the coalition said in an emailed statement.

At least 57 people – including 35 civilians, nine soldiers and 13 policemen – have been killed and more than 1,000 families displaced since the fighting began, provincial government spokesman Omar Zwak said. He said dozens of militants also had been killed, but he could not give a figure.

Taliban spokesman Qari Yousef Ahmadi claimed responsibility for the attacks in a statement sent to the media.

Karzai called on the Taliban not to kill innocent civilians. The government also approved about $90,000 for relatives of those who had been killed or wounded in the conflict as well as other civilians who have suffered, the presidential palace said.

In other violence Wednesday, a roadside bomb killed two policemen, including a district police chief, and wounded three others Wednesday in the eastern province of Ghazni, said deputy provincial police chief Col. Asadullah Ensafi. Taliban spokesman Zabihullah Mujahid claimed responsibility for that attack.

A bomb hidden in a wheelbarrow and detonated by remote control near a government building in the northern Faryab province killed four civilians and wounded 13 others, according to police spokesman Sayed Massoud Yaqoubi.

Faiez reported from Kabul. Associated Press writers Kim Gamel in Cairo and John-Thor Dahlburg in Brussels contributed to this report.

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