Fatah and Hamas clashed at Cabinet ministries, universities and security headquarters Saturday in defiance of a truce that was to have calmed the seething Gaza Strip.

The cease-fire agreement was announced late Friday on the deadliest single day of battles between the two sides, who have been fighting for control of the Palestinian government since the Islamic militant Hamas ousted Fatah from power in last year's elections.

Palestinian officials said the deal was approved by Palestinian President Mahmoud Abbas of Fatah and Hamas' supreme leader, Khaled Mashaal. But the cease-fire — the second announced this week — showed no signs of taking hold.

Gunbattles raged across Gaza after the truce was announced, continuing through the night and early Saturday. With no casualties reported overnight, some Gazans, who had spent the previous two days huddled at home for safety, were emboldened to leave their houses to go to work.

But 12 people had been wounded by late morning, hospital officials said, and Fatah said Hamas had kidnapped 40 of its security officials at roadblocks. Hamas reported one of its followers had been kidnapped.

Factional kidnappings have become a routine part of the Gaza landscape, but so far abducted men have been released quickly and unharmed.

In Gaza City, the coastal strip's largest town, Fatah gunmen stormed the Agriculture Ministry, ransacking offices and stealing computers, servers and official documents, said Agriculture Minister Mohammed al-Agha.

Fatah-affiliated security officials said nothing was stolen or destroyed, and denied al-Agha's assertion that gunmen opened fire from the building's rooftops.

Officials at the Hamas-run Communications and Postal Ministry said Fatah gunmen fired two rocket-propelled grenades at the building. Gunbattles also erupted around the Interior Ministry, which Hamas controls, and the Fatah-dominated National Security headquarters.

Universities also continued to be the site of clashes. Armed men at Islamic University, a Hamas stronghold, traded fire with Fatah fighters who took up position on the rooftop of nearby al-Azhar University and surrounding buildings. In southern Gaza, gunmen stormed the Fatah-affiliated Al-Quds University campus in the town of Rafah, torching the student council building, university officials said.

Gunmen in Gaza City stopped cars and searched them for rivals.

Even before the gunfire intensified, the streets of Gaza City had been almost empty. And the U.N. said it would not reopen its schools in Gaza on Saturday after a midyear recess, as scheduled, because of the fighting — a decision that kept nearly 200,000 students at home.

More than 100 Palestinians have been killed in internal violence since Hamas, which rejects Israel's right to exist, won parliamentary elections a year ago and wrested power from Fatah, which advocates peacemaking with the Jewish state.

On Friday alone, the day's death toll reached 17, including four children, and more than 200 people were wounded. Casualties were so high that hospitals ran out of ambulances to transport the dead and wounded, and blood supplies were running low.

In Washington, the so-called Quartet of Mideast negotiators met on Friday to explore ways to jump-start peacemaking between Israel and Abbas despite the latest round of Palestinian factional violence.

"There's simply no reason to avoid the subject of how we get to a Palestinian state," Secretary of State Condoleezza Rice said after meeting with foreign ministers from the European Union, United Nations and Russia.