Gunmen shot dead a Hamas commander in the Gaza Strip today and the Islamist group blamed a Fatah-dominated security service for the first killing in the territory since a ceasefire went into effect overnight.
Hospital officials in the southern town of Khan Younis said Hussein Shabasi was shot in the head.
A spokesman for Hamas's armed wing said he was killed by the Preventive Security Service, most of whose members belong to President Mahmoud Abbas's Fatah faction. The security service denied any connection with his death.
The ceasefire had appeared to be holding, bringing people out of their homes for the first time in five days as shops reopened and traffic again clogged Gaza's narrow streets.
The truce took effect after Prime Minister Ismail Haniyeh of Hamas met an aide to Abbas on yesterday in a bid to stem a surge of fighting in which at least 30 Palestinians were killed.
The internal violence that began on Thursday was the fiercest since Islamist Hamas, which rejects peace talks with Israel, trounced the more moderate Fatah in an election last year, triggering a Western aid embargo.