Palestinian militants briefly kidnapped three foreign church workers, including an American, while other gunmen set a Palestinian government building ablaze -- violence similar to the internal strife that sparked a government crisis earlier this month.

Five gunmen seized the foreigners-- an American, a Briton and an Irishman who had been doing missionary activity in Nablus for about three weeks -- Friday evening near their apartments, Palestinian security officials said.

No reason was given for the abduction. Officials said the kidnappers belonged to a renegade group of the Al Aqsa Martyrs' Brigades (search). The main militant group joined Palestinian security authorities in searching for the hostages, who were taken to the Balata (search) refugee camp.

The men were released after about three hours, but details were sketchy. The hostages were taken to the Palestinian intelligence headquarters. They declined to speak to reporters, and their identities were not released.

State Department spokeswoman Joanne Moore could not confirm the abduction but said they were looking into the reports.

Around the same time, about a dozen armed militants wanted by Israel burned a building of the local Palestinian government in Jenin to demand financial help from the Palestinian Authority, officials said.

The gunmen from the Al Aqsa Martyrs' Brigades, which is affiliated with Yasser Arafat (search)'s Fatah movement, broke into the building after work hours, fired automatic weapons into the offices and set the building on fire, said the officials.

The militants say they need public support since they cannot work and must remain under ground to avoid capture by Israel.

The violence, which appeared unrelated, was the most serious internal unrest in the Palestinian territories since Arafat and his prime minister, Ahmed Qureia, resolved a leadership crisis Tuesday by agreeing to share control of the Palestinian security forces.

A similar spate of kidnappings and attacks on the Palestinian Authority in the Gaza Strip earlier this month triggered the crisis, one of the toughest Arafat has faced in the last decade. Four French volunteers were among those briefly kidnapped in Gaza.

Earlier Friday, Israeli helicopters destroyed a bomb-making factory in a crowded district of Gaza City, gutting a building owned by a young mother who blew herself up in a suicide bombing early this year.

Palestinian medics said two bystanders were injured when one missile slammed into the middle floor of a three-story building, sending a fireball high into the night sky. The building was empty.

Israel said the metal shop in the building was used to build bombs for the Hamas militant organization. Palestinian officials said it was a factory for car batteries.

Also Friday, Israeli troops shot and killed several Palestinians near the town of Bureij who were planting explosives near an Israeli crossing with the Gaza Strip, Israeli military officials said. Both Israel Radio and Army Radio reported four Palestinians were killed.

Earlier, Israeli troops fired on Palestinians mourning the death of a militant leader in the Gaza Strip, killing a 12-year-old boy, hospital officials said, while Palestinians fired a salvo of missiles at an Israeli town.

The rocket attack came just hours after Israeli forces expanded their pre-emptive operations in northern Gaza to end the harassment of the town of Sderot and Israeli settlements in Gaza.

The escalation of attacks by the crude homemade Qassem rockets threatens to complicate Prime Minister Ariel Sharon's plans to withdraw troops and Jewish settlers from the Gaza Strip before October 2005. About 60 rockets have hit Israeli settlements in Gaza and across the border so far this month.