Gunmen from Fatah and Hamas exchanged gunfire in Gaza City tonight, witnesses said, further straining a shaky cease-fire between the rival Palestinian movements.
Hamas said a Fatah activist had shot and wounded a Hamas armed activist. Witnesses said the shooting triggered the ensuing gun battle.
It was not immediately clear if there were any casualties from the clash.
Earlier today, Palestinian President Mahmoud Abbas said today he would press on with early elections as a truce between his security forces and the Hamas government came under strain in the Gaza Strip.
British Prime Minister Tony Blair, speaking after meeting Mr Abbas in the West Bank city of Ramallah, said the international community should try to put together in the coming weeks a package of assistance to help the moderate leader.
Internal fighting, already at its worst level in years, escalated after Mr Abbas called on Saturday for fresh elections, a move intended to break political deadlock with the Hamas Islamists and get Western sanctions on their government lifted.
A truce deal was struck late today, but sporadic violence soon broke out again in impoverished Gaza.
Gunmen killed an activist from Mr Abbas's Fatah faction and wounded eight others in north Gaza, Fatah sources and a hospital official said. Fatah blamed the attack in the Jabalya refugee camp on Hamas. The Islamists said Fatah opened fire first.
A Palestinian security source said Hamas gunmen abducted nine Fatah activists during the day. Hamas said the abductions were triggered when Fatah abducted one of its members.
In Ramallah, Mr Abbas showed no sign of backing down.
"As I told you in my speech, I am determined to go back to the people," Mr Abbas said in a joint news conference with Mr Blair. "We have been in a crisis for nine months. People cannot wait for long. People are suffering from the economic social and security situation."
Mr Abbas insisted his Fatah movement was still open to the formation of a unity government and said this was the "best way forward".