Jerusalem. Israel says it is "preparing all options”, including a possible ground offensive, against militants in the Gaza Strip, as air strikes and rocket attacks between the two sides continue.

Israel says it hit "40 terror sites” on Tuesday. Palestinian officials say 11 people were killed.

Meanwhile, some 100 rockets have been fired at Israel by militants in Gaza.

Palestinian President Mahmoud Abbas has demanded that Israel end its military campaign.

Israel should "immediately stop its escalation and the raids on Gaza”, Mr Abbas said in a statement published by the official Wafa news agency.

Israel says it will pursue its offensive until rocket fire stops, warning a ground operation has not been ruled out.

"We have to be prepared for that option,” Israeli military spokesman Lt Col Peter Lerner told the BBC.

Lt Col Peter Lerner: Israel ‘no alternative’ but airstrikes

"We have to be prepared for that escalation. And indeed we are preparing. We have called up some reservists and we are taking the necessary steps around the Gaza Strip to be prepared for that option.”

Palestinian medics said at least three people were killed in an air strike on a car in Gaza City on Tuesday, the BBC’s Hamada Abuqammar reports.

An Israeli military spokesman said: "We can’t confirm number of casualties, but we can say that hits were identified.”

Another person died at a refugee camp in central Gaza, the health ministry said, while initial reports suggested that at least seven people were killed when a missile hit a house in the southern city of Khan Younis. The Israeli military said the houses that had been targeted belonged to Hamas members involved in launching rockets or other militant activity, and that they had been used as operations rooms.

Overnight strikes on facilities in Gaza left at least 15 Palestinians injured, Palestinian medical sources said. There have been no reports of Israeli casualties.

After a brief lull, militants continued to fire rockets at cities and towns in southern Israel on Tuesday, including Ashdod and Ashkelon. Israel says its operation, dubbed Protective Edge, will be expanded in the coming days and that 1,500 reservists have been called up.