The Tulkarem head of the Al-Aqsa Martyrs Brigades, an armed offshoot of Yasser Arafat's Fatah movement, was killed along with one of his lieutenants by Israeli forces in that northern West Bank town today, Palestinian witnesses said.
They were among five Palestinians killed by Israeli forces in military attacks in the West Bank and Gaza Strip today.
The events provided a violent backdrop to a US announcement of meetings in Washington later this week with Palestinians on ways to end 22 months of bloodshed.
Hamas said an Israeli sniper shot dead Hussam Hamdan (27), a senior member of its military wing in the southern Gaza Strip.
Hamas said it would avenge his death. Hamdan had escaped two previous Israeli attempts to kill him.
Earlier today, Israeli troops backed by 30 tanks pushed two kilometres (one mile) into Palestinian-ruled territory in the northern Gaza Strip, raiding the village of Beit Lahiya, where the army said it detained three militants.
By the time the Israelis started pulling out several hours later, a 29-year-old policeman lay dead from Israeli fire and two Palestinians were wounded, hospital sources said.
In Bethlehem, Israeli forces detained Yehya Damsa (42) commander of the Al-Aqsa Martyrs Brigades in the city. The group has carried out scores of suicide attacks.
The latest violence erupted ahead of talks US Secretary of State Mr Colin Powell and other officials will hold with a Palestinian delegation in Washington tomorrow and Friday.
The talks will focus on "Palestinian civil reform efforts, a renewal of security cooperation (and) progress on political dialogue," US State Department spokesman Mr Philip Reeker said.