Palestinian forces loyal to President Mahmoud Abbas went on a rampage against the Hamas-led government Monday, riddling the parliament and Cabinet buildings with bullets and setting them afire to protest an attack on their comrades in the Gaza Strip.

The violence was the most serious in the West Bank since Hamas defeated Abbas' Fatah movement in legislative elections in January and raised doubts about calls for Palestinian unity by the rivals.

Abbas and Hamas have been locked in a bitter power struggle since the Hamas-led government took office in March. Abbas, a moderate who was elected separately, has taken steps to curb the Islamic militants' authority. The dispute has focused on control of the security forces.

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The Ramallah rampage erupted late Monday, hours after Hamas gunmen attacked a building belonging to the Fatah-dominated Preventive Security agency in Gaza.

"Every time they touch one of ours in Gaza, we will get 10 of theirs in the West Bank," said one Preventive Security man.

Firing wildly in the air, the security forces marched through the streets of Ramallah toward parliament. They were joined by hundreds of gunmen from the Al Aqsa Martyrs' Brigades, a pro-Fatah militia.

The crowd shot out the windows of parliament before storming the two-building Cabinet complex. The throng smashed furniture, water coolers and air conditioners, destroyed computers and tore up documents before setting one of the buildings ablaze.

No casualties were reported, but the buildings suffered heavy damage.

When a fire engine approached the Cabinet building, a gunman lay on the road, blocking its way. The fire gutted the building's fourth floor before it was contained. The crowd then set the second floor of the parliament building ablaze.

Later Monday, Palestinian gunmen opened fire at Palestinian legislative offices in the West Bank city of Nablus, where the Al Aqsa Martyrs' Brigades has a strong presence. It was not known who fired the shots.

Fatah gunmen also said they abducted a Hamas lawmaker, Khalil Rabei, after setting his office on fire. A few hours later, the militants said they had released Rabei. The claims could not be independently verified.

Most of the Palestinian infighting has occurred in Gaza, Hamas' stronghold. Monday's incident signaled that Fatah is now ready to move the conflict to its West Bank power center.

At the time of the rampage Abbas was in Gaza, where he has been holding negotiations with Hamas in hopes of ending the political deadlock. Neither Abbas nor Hamas officials immediately commented on the West Bank violence.

Internal tensions have heightened since Abbas scheduled a July 26 referendum on a plan calling for implicit recognition of Israel. Abbas has endorsed the plan as a way out of the stalemate. But Hamas objects to the vote.

In a conciliatory gesture, the Hamas-dominated Palestinian parliament on Monday pulled back from a plan to block the referendum, delaying a vote on the issue until June 20 to allow negotiations to continue. But the violence cast serious doubts on efforts to bridge the gaps.

The Ramallah violence was sparked by a daylong gunbattle in the southern Gaza town of Rafah. The fighting began during the funeral of a Hamas gunman who died from wounds sustained in a clash with Fatah-allied forces last week.

Witnesses said Hamas supporters in the funeral procession fired on the local Preventive Security building. Officers fired back, killing a Hamas gunman.

Enraged Hamas gunmen, joined by relatives of the dead man, surrounded the Preventive Security headquarters. A second shootout erupted in which Hamas fired a rocket-propelled grenade at the building.

Officials said 14 people were wounded, most of them Preventive Security officers, and a male bystander was killed in the crossfire.

Col. Yousef Siyam, chief of Preventive Security in Rafah, accused Hamas of carrying out a premeditated attack and called on Hamas' interior minister to investigate the "serious provocation."

Hamas officials accused the Preventive Security force of provoking the shootout.

Witnesses said members of Hamas' controversial new private militia participated in the fighting. Just last week, Hamas had pledged to withdraw the force to help ease tensions. Nineteen people have died in fighting between Hamas and Fatah loyalists since the force was deployed last month.

Seeking a way out of the infighting, Abbas last weekend scheduled the referendum on a plan calling for a Palestinian state alongside Israel, implicitly recognizing the Jewish state.

Abbas believes a unified political platform by Palestinian factions would help end crushing international sanctions against the Hamas-led government and allow him to restart peace talks with Israel.

Hamas, which is sworn to Israel's destruction, opposes the referendum vote. But it has entered a "dialogue" with Abbas over the plan. The sides were meeting late Monday when violence erupted in the West Bank.

Abbas is pushing forward with the referendum, despite calls for a delay following an explosion on a Gaza beach Friday that killed eight civilians.

Palestinians said an Israeli artillery shell caused the explosion, which has inflamed passions against Israel. Israel is conducting an investigation and has suggested its army wasn't responsible.

Israel-Palestinian violence has escalated since the beach explosion, with Hamas officially calling off a 16-month truce. Hamas militants have fired several dozen rockets at southern Israel, causing no damage or injuries, the army said.

Military officials said Israeli Defense Minister Amir Peretz postponed an air offensive against Gaza militants for a day or two to give the Palestinians more time to stop rocket attacks from the coastal territory.