The European Union on Saturday expressed concern at the worst Israeli-Palestinian violence in three years which left 14 Palestinians dead, calling on both sides to restore calm.

A statement from EU foreign policy chief Catherine Ashton said the bloc "is following with concern the recent escalation of violence in Gaza and in the south of Israel".

"I very much deplore the loss of civilian life. It is essential to avoid further escalation and I urge all sides to re-establish calm."

Medics said Saturday that Israeli air strikes on the Gaza Strip killed 14 Palestinians, including a militant group chief, after Palestinian militants fired at least 90 rockets and mortar rounds into southern Israel, according to an army spokeswoman.

The Palestinian barrage wounded four people, one of them seriously, Israeli military sources said.

Israeli media said that three of the casualties, including the badly wounded man, were agricultural labourers from Thailand working on a farm near the border with Gaza.

One of the retaliatory air strikes killed the head of the Popular Resistance Committees (PRC), Zohair al-Qaisi, and fellow member Mahmud Hanani, the ultra-hardline militant group said.

Al-Quds Brigades, the military wing of Islamic Jihad, said the strikes also killed 10 of its members.

France also called for restraint and a return to calm in a statement issued by foreign ministry spokesman Bernard Valero.

Paris was "greatly concerned by the new episode of violence in Gaza and southern Israel," especially as civilians were at risk, the statement said.

"We condemn the firing of rockets and the humanitarian consequences of this violence and deplore the civilian casualties," it added.