Four Palestinians -- including a senior militant and a college professor -- and an Israeli special forces officer were killed in fierce firefights early Tuesday in the West Bank city of Nablus, according to an Israeli military spokeswoman and Palestinian security sources and medical officials.

Two more Palestinians were killed during an attack on an Israeli military vehicle in the Gaza Strip, the Israeli spokeswoman said. The men were shot and killed as they ran toward an Israeli jeep while firing assault rifles and hurling grenades, she said. Two Israeli soldiers were injured by shrapnel during the incident, and explosive charges were found on the bodies of the dead men, she said.

The senior militant killed in Nablus, a key center for radical Palestinian groups about 28 miles north of Jerusalem, was identified by Palestinian hospital officials and in announcements blared from local mosques as Yamon Faraj, the West Bank military leader of the Popular Front for the Liberation of Palestine. One of Faraj's senior commanders in Nablus, Amjed Hanani, was also killed in the fighting, Palestinian officials said.

The killings occurred on the 11th day of an Israeli military operation against top Palestinian militants in Nablus that began June 26, when Israeli soldiers discovered an underground hideout in the center of the city and killed six senior leaders from three radical groups, including the West Bank heads of the al-Aqsa Martyrs Brigades and Islamic Jihad and the local chief of the Islamic Resistance Movement, or Hamas.

Late Tuesday, another militant -- Wael Araysha, 26 -- was killed when his M-16 rifle exploded inside his car near the Balata refugee camp, according to Palestinian security sources, who said they believed the weapon was booby-trapped and detonated by Israeli operatives. An Israeli security source said: "We had nothing to do with it. We believe it was a work accident."

Tuesday's fighting began shortly after midnight and was concentrated along Sekeh Street in Ein Beit Ilma, a refugee camp in the northwest of the city. Israeli and Palestinian accounts of the incident differed on several points.

An Israeli military spokeswoman said a team of elite naval commandos went into the neighborhood to arrest some wanted Palestinian militants and identified two of them entering a house. When the men realized that they had been spotted, she said, they fled from the building, then fired at the commandos from short range, killing Capt. Moran Vardi, 25, and wounding two others.

Soldiers returned fire and killed one of the gunmen. His companion escaped into a nearby apartment building and opened fire from the windows, then went to the roof and continued shooting, wounding another Israeli soldier, the spokeswoman said.

Israeli helicopters and tanks were called in for reinforcement, and a helicopter fired a missile at the gunman on the roof, wounding him, according to the spokeswoman, Maj. Sharon Feingold. She said the man managed to escape from the building, and soldiers shot and killed him on the street.

Palestinian medical officials said that at the start of the Israeli operation -- at about 12:30 a.m., while the hunt was on for the two militants -- Israeli soldiers with a loudspeaker ordered the residents of one building to evacuate. It was unclear whether the building was one of those the militants had entered.

The first to obey the order, medical officials said, were Khalid Salah, 54, a professor of electrical engineering at Nablus's An-Najah National University for 25 years, and his 16-year-old son, Muhammad. But when the pair opened the door to the street, the medical officials said, Israeli troops opened fire, mortally wounding them.

The medical officials and neighbors said that the Salah family pulled the pair back inside the building and telephoned for an ambulance, but that an emergency medical unit was prohibited from entering the area by Israeli soldiers who had declared the street a closed military zone.

Medical technicians reached the father and son at about 4 a.m., the officials said, and found them dead.

Three other Palestinians were injured during the fighting, Palestinian hospital officials said.

A statement by the university said that Salah earned his doctorate in electrical engineering from the University of California at Davis in 1985. A spokesman for the U.S. Consulate in Jerusalem said that Salah's wife said in a conversation Tuesday with consulate staff that he had a green card to work in the United States.

Feingold denied that Israeli troops had called for residents to evacuate any buildings in the area until the fighting was finished. "No one opened a door and was shot at," she said.

After the two militants were killed, Feingold said, residents of the building where the second gunman had taken shelter were ordered outside so troops could safely search the rooms. After that, the bodies of Salah and his son were brought out, but it was unclear when the pair was killed or by whom, she said.

Tahrir Hanani weeps over the body of her husband, Amjed Hanani, a member of the Popular Front for the Liberation of Palestine in Nablus who was killed in a firefight during an Israeli sweep for Palestinian militants.Smoke rises from a house blown up by Israeli troops in Nablus after the Army tagged it as a refuge for militants.