Israeli soldiers killed at least six Palestinian militants in overnight raids in the West Bank and Gaza Strip.
The brief operation just across the frontier in the northern Gaza Strip marked a new Israeli military response to the frequent Palestinian rocket launches at southern Israel.
Witnesses said Israeli commandos backed by a helicopter gunship killed four members of a Palestinian rocket squad as they were about to fire.
At least three of the dead were identified as members of the militant Islamic Jihad group and the fourth man belonged to the Force 17 presidential guard, who witnesses said rushed to the scene with medics to offer aid.
"The fighters were firing rockets into Israel in retaliation for the continued Israeli crimes and the assassination of Abu Hamza al-Majzoub in Lebanon," an Islamic Jihad statement said, referring to a car bombing that killed a senior official of the group in south Lebanon last week.
An Israeli army spokeswoman said the overnight fighting marked the first ground combat in Gaza since Israel withdrew its troops and dismantled 21 Jewish settlements there in August.
Israeli troops have on occasion ventured across the border fence to dismantle bombs, the army spokeswoman said.
In the West Bank, troops killed at least two gunmen in separate operations. An Islamic Jihad member was killed and three other militants wounded in the northern village of Qabatia.
In a Palestinian refugee camp near the city of Nablus, a wanted militant was shot dead and another wounded. Witnesses said a third militant was killed by troops in the town of Anabta. But the army denied operating in the area.
The persistent violence has complicated efforts by moderate Palestinian President Mahmoud Abbas to cajole the new Islamist Hamas government to accept peacemaking with Israel.