An Israeli aircraft attacked a training camp used by Palestinian militants in Gaza City on Friday, killing five militants, including four relatives of a top commander, Palestinian officials said.

Palestinian officials said the dead men were training at a base used by the Popular Resistance Committees, an umbrella group responsible for numerous rocket attacks against Israel. During five years of fighting, the Israeli army has killed dozens of militants in so-called targeted killings.

The airstrike scattered body parts and left pools of blood in a field just yards away from the home of Moumtaz Dourghmush, the top militant commander in the resistance committees. Dourghmush was not at the scene, but a brother and three cousins were among the dead, hospital officials said.

Abu Mujahid, an official with the militant group, said at least three missiles landed on the field as members were training. "God willing, this is not going to stop our heroic battle against the Zionists, and the blood is the fuel of our resistance and our reprisal is coming soon,"

The army confirmed it had targeted the Popular Resistance Committees, saying that militants were training for attacks against Israel. "The army will continue to track down those who support and are involved in terror attacks," it said.

Since the Hamas-led Palestinian government took office in late March, Israel has stepped up its military activity in Gaza in response to repeated rocket fire.

The rocket attacks have not caused any serious casualties, but have been deadly in the past. While not believed to be directly involved in the rocket fire, Hamas has refused to condemn the attacks or take steps to stop them.

The Popular Resistance Committees has claimed responsibility for much of the rocket fire. In the past, the group also has blown up Israeli tanks and is widely believed to be behind the deadly bombing of a U.S. diplomatic convoy in October 2003.

Earlier Friday, a Palestinian man was killed during a stone-throwing demonstration against Israeli troops in the West Bank city of Nablus, Palestinian medical workers said.

The army said troops entered the city to arrest a man wanted by Israel. It did not immediately comment on the report of the dead Palestinian.

The Palestinian, 19, was shot and killed when a group of protesters threw stones at soldiers after the arrest, witnesses said. Palestinians said four men, including two members of a militant group, were arrested in the raid.