The Israeli military fired a barrage of artillery and missiles at the Gaza Strip on Tuesday, hitting two offices of the Al Aqsa Martyrs' Brigades and a bridge the army said was used by militants to reach areas where they fire rockets.

Hours later, about 40 gunmen took over an election office in the neighborhood of A-Ram just outside of Jerusalem, demanding that the ruling Fatah Party include more representatives of the neighborhood in its list for parliamentary elections on Jan. 25, said Ziyad Al-Bakri, the coordinator of the office.

Earlier in the day, about two dozen armed Al Aqsa militants took over the governor's office and two other government buildings in the northern Gaza Strip for several hours. The takeover was the latest outbreak of lawlessness that has undermined the rule of Palestinian leader Mahmoud Abbas.

Israel's pre-dawn aerial strikes were part of the army's attempt to halt rocket fire on Israeli towns bordering Gaza. Prime Minister Ariel Sharon has approved a buffer zone in northern Gaza, although the army said it has not yet implemented the plan — which includes firing on anyone who enters the area — and was unlikely to on Tuesday.

The army has been destroying roads and other installations used by militants to reach areas that put Israeli towns within range of their highly inaccurate, homemade rockets. The bridge destroyed Tuesday has been targeted before.

Since Israel's withdrawal this summer from the Gaza Strip, more Israeli towns — including the city of Ashkelon — have come into rocket range. Earlier this month, a rocket landed near Ashkelon's power plant and a fuel depot.

The offices of Al Aqsa — a group with links to the ruling Fatah party — were targeted because militants used them to meet, plan and recruit, the army said. But Palestinians said the offices, empty during the airstrike, were used for social and educational purposes.

One missile was fired into each building, leaving holes in the outer walls, shattering windows and burning furniture, Palestinian witnesses said.

Israel says Abbas has failed to act against the militants and halt their rocket fire, forcing the army to deal with the problem itself.

Abbas, who reached a cease-fire deal with the militants last March, has preferred persuasion over coercion, fearing a crackdown could lead to civil war. He also says that his security forces, destroyed during five years of fighting with Israel, do not have the means to take on the militants.

But ordinary Palestinians yearn for law and order, as chaos reigns in Gaza and the West Bank.

At A-Ram, the gunmen said they would stay in the offices until elections on Jan. 25 if necessary to get their demand for more representatives on the Fatah list, and al-Bakri said the takeover was a sign that Palestinian militants were gaining the upper hand in the streets.

"I believe that this threatens the elections and the political situation in the West Bank and Gaza Strip," said Al-Bakri, who planned on leaving the office with his staff at the end of the day. "I think the situation will only get worse."

Earlier in the day, gunmen took over the governor's office, the Education Ministry and a religious court near the town of Beit Lahiya in northern Gaza — the latest incident in a growing trend of gunmen using threats and violence to demand jobs.

The gunmen stormed the buildings armed with hand grenades, rocket-propelled grenades, rocket launchers and automatic rifles. Police stationed in a building next door watched the gunmen enter, witnesses said, and did nothing.

Later, security forces surrounded the governor's office and Fatah officials, mediating by phone, tried to persuade the gunmen to leave, while two Israeli helicopter gunships hovered overhead.

"This is a first message, the next message will be burning buildings," Abu Hussam, an Al Aqsa militant, told reporters in Gaza.

The gunmen left 4 1/2 hours after taking over the buildings, saying they had received promises from the Palestinian leadership to discuss job opportunities. Abbas has been criticized for giving into the demands of gunmen, encouraging more mayhem.

The showdown came as both Israel and the Palestinians geared up for separate election campaigns. Security issues are a focus in both campaigns, with Israelis demanding an end to rocket fire and Palestinians seeking order.