At least eight Palestinians have been killed and 20 injured in two separate Israeli strikes in the northern Gaza Strip, Palestinian officials have said.
Israel said the militants killed had been preparing a rocket strike
Four militants, believed to be members of the Army of Islam, died when a missile was fired at their vehicle as they drove through eastern Gaza City.
The Israeli military confirmed its aircraft had carried out a raid.
In a separate incident, Israeli tank fire killed four Palestinians in Beit Hanoun, local medical officials said.
At least three of those killed in the reported shelling of a house in the town have been named as civilians. Witnesses said the fourth victim was a gunman.
The two strikes came hours after Israel warned it was on the verge of launching a large-scale incursion into Gaza.
"We are getting closer to carrying out a widespread operation in Gaza which, for many reasons, has not taken place in the past weeks," Defence Minister Ehud Barak told Israel's Army Radio.
Mr Barak said the move would be in response to continued rocket attacks by Palestinian militants and his government's desire to weaken the Islamist movement, Hamas, which seized control of the coastal territory in June.
The BBC's Aleem Maqbool says previous operations in recent months have left dozens of Palestinians dead - mainly militants, but many civilians too - and the rockets keep being launched.
One of the militant groups, Islamic Jihad, has said it will keep firing the rockets in response to Israeli killings and what it calls human rights abuses.
The Israeli military said the four men killed in the airstrike in Gaza City had been preparing to launch rockets across the border into southern Israel.
Witnesses said the jeep in which the militants were travelling was struck by an Israeli missile as it crossed a crowded intersection in the eastern Zeitoun neighbourhood.
The force of the explosion shattered the windows of several nearby buildings and sent shrapnel flying into other cars.
Hamas said one of those killed was Ayman Daloul, a field commander of the Army of Islam.
The Army of Islam is a small Islamist group that splintered from the Popular Resistance Committees.
It was responsible for holding BBC correspondent Alan Johnston hostage for 16 weeks this year and claims to be one of three groups holding the captured Israeli soldier, Cpl Gilad Shalit.