Three Palestinian militia chiefs have been killed by Israeli troops in the West Bank town of Tulkarm.
Local sources said they were from the al-Aqsa Martyrs Brigade, a militant offshoot of Yasser Arafat's faction.
Israeli army operations in northern Gaza are continuing for a third day - with troops blowing up buildings in Beit Lahiya.
A 16-year-old boy was killed by Israeli fire bringing the death toll in the area to 14 people.
A centre for handicapped people was among the buildings that was blown up in Beit Lahiya, AFP news agency reported. An Israeli army spokesman said the building was unoccupied at the time.
The Israelis say the operation is aimed at preventing Palestinian militants from firing rockets and mortars into nearby Jewish settlements.
Violence in Gaza has surged since Israeli Prime Minister Ariel Sharon announced unilateral plans to withdraw Jewish settlements from the coastal territory as part of his disengagement plan.
The recent killings of Hamas leaders Sheikh Ahmed Yassin and Abdel Aziz al-Rantissi have also led to increased tensions in Gaza.
Analysts say Israel has stepped up its attacks ahead of the planned pullout so as not to allow Hamas to claim it as a victory for the resistance.
Although the focus remains in Gaza, Thursday's violence in Tulkarm follows a pattern of raids targeting local militant cells in the West Bank.
Witnesses said soldiers moved into Tulkarm at dawn and heavy gunfire broke out.
An army spokeswoman said troops had engaged the men on the edge of the town and had shot them at close range.
The army spokeswoman, quoted by Reuters, said the militants approached the soldiers, aiming rifles in their direction at close range.
"It was a matter of seconds as to who would open fire first," the spokeswoman said.
On Wednesday, Mr Sharon promised Israel would "not let up" on the perpetrators of "terror".
"In that way we got rid of the first murderer (Sheikh Yassin killed on 22 March), and in that way a few days ago we got rid of the second murderer (Rantissi), and that is not the end," he said in a speech at the port city of Ashdod - the site of a 14 March suicide bombing.
In parliament on Thursday, Mr Sharon brushed aside the latest poll of members of his Likud party which showed growing opposition to his plan to leave Gaza and dismantle isolated settlements in the West Bank.
"Anyone who wants Israel to initiate and not be dragged, to lead and not be
led, must support the disengagement plan," Mr Sharon said.
Likud will hold a binding referendum on the plan on 2 May.
At least 15 Qassam rockets have landed over the boundaries of Gaza in recent days, injuring five Israeli civilians.
On Wednesday BBC correspondent Peter Greste witnessed a column of tanks backed by helicopter gunships entered Beit Lahiya, as soldiers searched houses looking for militants involved in firing the rockets.
Northern Gaza has been wracked by violence in recent days
Palestinian youths fought the tanks and armoured vehicles with whatever came to hand; stones, home-made grenades and smuggled Kalashnikovs.
Our correspondent saw angry young teenagers run to within a few metres of the tanks to toss whatever they had in their hands.
Ambulances ran a constant shuttle for the dead and wounded, some as young as 14, our correspondent said.
About 40 Palestinians were wounded during the incursions.
An Israeli army spokesman said: "Everyone we hit was either armed or planting bombs."