JABALIYA, Gaza Strip — A roadside bomb on Tuesday struck the convoy of the Palestinian prime minister during a rare visit to the Gaza Strip, causing no serious injuries but throwing an already troubled reconciliation process between rival factions into deeper turmoil.

Prime Minister Rami Hamdallah had just arrived from his West Bank headquarters to attend a ribbon-cutting ceremony for a new water-treatment plant when the bomb went off. Although there was no claim of responsibility, Palestinian officials accused Gaza militants of trying to assassinate Hamdallah. Gaza’s ruling Hamas group denied involvement.

The blast took place at a time of deadlock in reconciliation efforts between Hamdallah’s Fatah party and Hamas, which has controlled Gaza since ousting Fatah forces in 2007. It also cast a shadow over a special White House meeting where international donor nations were set to discuss the dire humanitarian situation in Gaza.

Hamdallah, a soft-spoken former university dean appointed by President Mahmoud Abbas five years ago, went on to inaugurate the long-awaited sewage plant project. But he quickly returned to the West Bank, where he vowed to press ahead with reconciliation efforts.

“This will not deter from seeking to end the bitter split. We will still come to Gaza,” he said.

He said the attack underscored the need for the Palestinians to unify under a single authority. Hamas has ceded some government functions and control of Gaza’s borders, but it has refused calls to disarm and let Palestinian Authority security forces take over.

“How can a government overtake Gaza without maintaining security? We ask Hamas one more time to empower the government,” he said. “Without security, there won’t be a government or an authority.”

Hamas condemned the attack, calling it a crime and an attempt to “hurt efforts to achieve unity and reconciliation.” It promised an “urgent” investigation.

Witnesses said the bomb was planted under an electric pole on Gaza’s main north-south road and went off shortly after Hamdallah’s 20-vehicle convoy had entered through the Israeli-controlled crossing.

“I could not see anything because smoke and dust filled the air. When the smoke cleared, the explosion was followed by heavy gunfire, apparently from police securing the convoy,” said a witness, who declined to be identified because of security concerns. “When the dust cleared, I saw people running everywhere, and police were running around.”

Two vehicles were disabled by the blast, while at least four others were damaged, with windows or sunroofs blown out. One had streaks of blood on the door. Hamdallah said six bodyguards required medical attention.

In the West Bank, Abbas blamed Hamas for the blast. But his security chief, Majed Farraj, who was in the convoy and was another potential target of the blast, said it was “too early” to say who was responsible.

There is a long list of potential attackers. While Hamas officials strenuously denied involvement, there are elements within the group that do not want to cede power and oppose the reconciliation process. More radical militants, inspired by the Islamic State group, also operate in Gaza. Some even suggested that the Palestinian Authority had staged the incident to shore up Hamdallah’s calls for Hamas to disarm.