Ismail Haniya, the Palestinian prime minister, vowed on Saturday in Gaza City to end the security chaos "using law and order" and by "withdrawing armed civilians from the street to end this dangerous situation".
"What happened was dangerous and must not be repeated," Haniya said as Aljazeera reported that men from al-Aqsa Martyrs Brigades had seized the offices of the Interior Ministry in Nablus in the West Bank.
Friday's clashes broke out when members of the Popular Resistance Committees (PRC), an armed group that often fires rockets at Israel, accused Palestinian security forces close to Abbas of helping Israel kill a field commander in a car blast.
"The culture that dominated the Palestinian street in past years is a culture that needs time in order to turn into a culture that keeps law and order and does not resort to using arms under any condition," Haniya added.
The declarations came after clashes between fighters and supporters of Mahmud Abbas' Palestinian Authority on Friday left three people dead and 36 wounded.
Appeal to world
"There is an escalation against the Palestinian people aimed at breaking them and the government," Haniya said.
"We ask all the countries in the world to assume their responsibility and face this escalation against our people," he said.
But armed men from Fatah fired off guns in a show of force in Gaza on Saturday, defying Haniya's orders to stay off the streets.
Al-Aqsa Martyrs Brigades men
took over a PA office in Nablus
They accompanied Samir al-Mashharawi, a Fatah leader, from the Gaza border with Egypt to his home. Later they dispersed.
"We will co-operate to end armed displays and I call on Fatah men not to be dragged into sedition," al-Mashharawi said.
The fighters demanded that Haniya arrest members of the PRC whom they blamed for Friday's deadly clashes.
About 300 armed men shot repeatedly into the air as al-Mashharawi threatened to take measures if Haniya failed to arrest a leader of the PRC.
"We in Fatah will not allow this person to escape punishment," al-Mashharawi said.
Israel has denied any involvement in Friday's assassination.
The PRC, for its part, said it had agreed to follow Haniya's call and Rashid Abu Shbak, Palestinian preventive security chief, met with the interior minister and said the armed men had left the streets.
"I do not think there are gunmen anymore," he said. "The incident is over at the moment and I hope there will be no more consequences".
Israeli artillery meanwhile bombarded a unilaterally declared no-go zone in the northern Gaza Strip after Palestinian fighters fired three rockets at Israel on Friday night, with bombers hitting targets in Gaza City.
A PRC commander was killed in a
car-bomb blast on Friday in Gaza
Four more rockets were fired on Saturday afternoon without causing any casualties, the Israeli army said, while the air force dropped propaganda pamphlets in Arabic on the territory.
The armed faction Islamic Jihad said it had launched three rockets at the southern Israeli town of Ashkelon in a statement sent to AFP.
A Katyusha rocket was fired from Gaza at southern Israel for the first time on Tuesday. Although it caused no injuries, Shaul Mofaz, the Israeli defence minister, said it was "a serious development which demanded a strong and decisive reaction".
Israel believes the Katyusha rocket was one of a batch smuggled into the Gaza Strip over its border with Egypt, an Israeli Defence Ministry spokesman said.