GAZA CITY, Gaza Strip ? The killing of a 10-year-old Palestinian girl in a Gaza schoolyard Monday prompted Islamic militants to fire mortar shells at Jewish settlements and endangered an unofficial cease-fire between Israelis and Palestinians.

The renewed violence overshadowed a meeting between top Israeli and Palestinian security officials who worked Monday to arrange a handover of several West Bank towns to Palestinian control. Israeli officials said the security meeting ended with no accord on a handover.

Although the circumstances of Norhan Deeb’s death were unclear, the violence strained the recent atmosphere of goodwill between Israeli Prime Minister Ariel Sharon and new Palestinian leader, Mahmoud Abbas.

The girl was killed in the courtyard of a U.N. school in the Rafah refugee camp near the Egyptian border, a frequent flashpoint of violence between Israeli troops and Palestinian gunmen.

Palestinian witnesses said the gunfire came from a nearby Israeli military position along the border.

The Israeli military said it checked the claims and found two cases in which soldiers opened fire, but neither was in the area where the girl was shot. “According to our examination, the girl apparently was not shot by Israeli army gunfire,” the military spokesman’s office said.

A military official, speaking on condition of anonymity, said Palestinian revelers had been shooting into the air in the area, celebrating their return from the Hajj pilgrimage to Mecca.

Residents, however, said there were no such celebrations.

Johan Eriksson, a spokesman for the U.N. Relief and Works Agency, said U.N. officials weren’t able to definitively identify the source of the gunfire, but that all signs pointed to the Israeli troops.

Hours later, Palestinian militants fired at least six rounds of mortar shells at Jewish settlements in Gaza, damaging one house in the Neve Dekalim settlement, the Israeli army said. The Islamic group Hamas claimed responsibility, saying it was avenging the girl’s death.

Later Monday, Hamas issued a statement threatening to retaliate against Israel “if the crimes continue,” implying that it would hold its fire if no further violence occurs.

Flowers are seen on the desk of Norhan Deeb in the B school in Rafah refugee camp, southern Gaza Strip. Deeb, 10, was killed Monday on the grounds of her United Nations school in Rafah by what Palestinian officials said was Israeli tank fire.