A leader of Islamic Jihad is believed to have been killed in a strike on a building in Gaza City.
According to the Associated Press, the IDF struck the media centre used by Hamas' communications wing for the second time on Monday.
The news agency named the assassinated terrorist as Islamic Jihad's Ramez Harb, a key figure in the Al Quds Brigades.
The IDF Spokesperson said on Twitter: "A short while ago, the IDF targeted a cadre of senior Palestinian Islamic Jihad operatives who were hiding in a media building in Gaza.
"A direct hit was identified on the target. Four senior members of Palestinian Islamic Jihad were known to have been in the media building."
Terrorist groups have continued firing rockets across the border, with 12 rockets fired at civilian populations in southern Israel in a ten-minute period. One landed beside a school in Ashkelon, although classes had already been cancelled because of the threat. The school has been hit twice since fighting began on Wednesday.
Twelve people were killed in air strikes on Gaza on Monday morning, along with four terrorist operatives. The death toll is now said to stand at 90 Palestinians, with nearly half thought to be terrorists.
Ban Ki-Moon, the UN Secretary General, has travelled to Egypt to push for a ceasefire and "appeal personally for ending the violence and contribute to ongoing efforts to that end".
He added: "Any further escalation will inevitably increase the suffering of the affected civilian populations and must be avoided."
The Quartet Middle East envoy Tony Blair is also in the region and has met Israeli President Shimon Peres for talks.
Speaking on Channel Four's Daybreak programme on Monday, Israeli envoy to the UK Daniel Taub said that Israel had to protect the lives of its citizens and "do what any responsible country would do".
He said Israel did not want to have a ground operation. "The answer is for Hamas to stop firing and to have a genuine ceasefire that is going to last."