Jerusalem:  Prime Minister Benjamin Netanyahu on Sunday warned that Israeli air assaults against Gaza would go on "as long as it is necessary", as the death toll in renewed violence in the Palestinian coastal territory rose to 18.

"We have exacted from them a very high price. We will continue to operate as long as it is necessary," Netanyahu told his ministers at a weekly cabinet meeting asserting that the country was on "high alert" to prevent any terror attack.

Israeli air strikes on Gaza today killed three, including a 12-year-old boy, as violence on the troubled border continued for a third day.

Medical spokesman in Gaza, Adham Abu Salmiya, said Ayoub Useila, 12, was killed in the Jabaliya refugee camp and his seven year old cousin injured in an attack. Israeli jets also pounded the Zeitoun neighbourhood of Gaza City, killing Ahmad Deib Salim, 24.

The third victim of Israeli air strikes was Adel al-Issi, 52, a farmer who was also killed in the Gaza City, Abu Salmiya said, bringing the death toll since Friday evening to 18.

Israel Defence Forces (IDF) Chief of Staff, Benny Gantz, said more than 120 rockets were fired at Israel since Friday and his forces would continue to retaliate with force to protect Israeli citizens.

Gantz noted that 20 per cent of the rockets fired from Gaza on major population centres in Israel's south were intercepted by the Iron Dome anti-missile system. "The IDF has demonstrated accurate interception abilities," he said.

"The IDF has retaliated and will continue to retaliate  with force and sensitivity against any firing directed at Israel. Hamas and other terror groups continue to gain strength at an alarming rate. We do not seek escalation but
Hamas controls Gaza," Gantz stressed.

Violence between Israel and Gaza militants erupted on Friday afternoon when an Israeli strike killed the leader of the ultra-hardline Popular Resistance Committees, Zohair al-Qaisi, sparking a bloody cross-border exchange.

Netanyahu justified the attack saying "he was in the midst of planning another attack that was directed at our southern border with Egypt" and Foreign Minister Avigdor Lieberman called him "a ticking bomb".

Meanwhile, Egypt was making efforts to halt a further escalation in violence.

"Egypt is in a race against time in order to halt hostilities as soon as possible to avoid further escalations," Egyptian ambassador to the Palestinian territories, Yasser Othman, told the Palestinian Ma'an News Agency.