Israeli airstrike kills 4 Gaza militants

In a separate incident, Palestinian rocket fire injured one Israeli.

Both sides say they would like to preserve the truce, which expires next month. But with violence escalating over the past two weeks, the cease-fire appears to be unraveling.

The militants killed in the airstrike were from a small Hamas-allied group known as the Popular Resistance Committees. Abu Attaya, a spokesman for the group, said the four were firing mortars when they were killed.

Abu Mujahed, another spokesman for the PRC, said his group is pulling out of the truce, and Hamas spokesman Fawzi Barhoum threatened retaliation for the killings.

"Today's crime will not pass without punishment," he said.

After the strike, dozens of onlookers converged on the bodies of two of the dead men shouting "God is great." They then carried the bodies, one wrapped in a blanket, to a nearby civilian car.

At sundown a rocket launched from Gaza hit a house under construction in the battered Israeli border town of Sderot, slightly injuring a resident, police and media reports said. Palestinians launched two other rockets earlier in the day but no one was hurt, the military said.

According to the Israeli military's count, Palestinians have sent more than 170 rockets and mortars flying at Israel since the violence resumed nearly two weeks ago. Israeli troops have killed 15 militants, and two more died in unclear circumstances.

Israeli leaders signaled they have not given up on the fragile cease-fire.