GAZA, March 10 (Nidal al-Mughrabi/Reuters) - Israel killed four Gaza militants on Saturday as violence sparked by the death of a militant leader a day earlier escalated with gunmen firing more than 90 rockets at Israel, injuring four people, Israeli and Palestinian officials said.

In all Israel, has killed 14 militants in aerial strikes launched since Friday, Hamas medics said. In the latest attack, a gunman was killed on a motorcycle and another was critically wounded and later died of his injuries, medics said.

Two other militants from the Islamic Jihad group were killed in predawn strikes on Saturday, officials in Gaza said.

Nabil Abu Rdainah, a spokesman for Palestinian President Mahmoud Abbas, blamed Israel for the violence and called for Western intervention to try and halt any further escalation which threatened to complicate rife tensions along the restive Israeli-Gaza frontier and their common border with Egypt.

This Israeli escalation in Gaza is completely condemned and we urge the world community, and the Quartet (of Middle East power brokers), especially the United States, to put enough pressure on Israeli government to stop this escalation, Rdainah told Reuters television.

After weeks of relative calm, violence along the Israeli-Gaza frontier escalated on Friday when Israel blew up a car in Gaza City, killing two militant leaders.

Israel said one of the militants killed on Friday had been involved in plotting a cross-border attack from Egypt. Israeli media reports said he had also been closely involved in the 2006 capture of Israeli soldier Gilad Shalit, freed as part of a prisoner swap in October.

ISRAEL TARGETS WEAPONS

An Israeli military statement said the latest air strikes had targeted two weapons manufacturing sites. The strikes were launched in response to rocket fire from Gaza that injured four people in Israel, including one man, who is reported to be in a serious condition, it added.

Israeli media said the seriously injured man is a worker from Thailand.

The sounds of explosions and rocket fire reverberated across coastal Gaza and parts of southern Israel early on Saturday. Some half a million people were urged to remain indoors and keep bomb shelters open, and public events were cancelled.

Militant groups in Hamas-ruled Gaza vowed to exact revenge for the killings. According to the Israeli military, more than 90 rockets have been fired at Israel since Friday, including 25 longer-range Grad rockets intercepted by Israel's Iron Dome missile interceptor system.

Islamic Jihad and the Popular Resistance Committees (PRC) claimed responsibility for most of the rockets and mortar shells fired which they also said totaled more than 70.

Israel launched some half a dozen air strikes at militants in Gaza on Friday, killing 10.

Hamas, which refuses to recognize Israel, did not claim responsibility for any of the missile attacks on Israel, and there were no reported civilian fatalities in Gaza, factors which may keep the violence from escalating.

However, Israel says it holds Hamas responsible for any attacks launched from its territory.

Around six Palestinians among 17 people wounded in the Israeli attacks have been identified by medics as civilians.

Hamas seized control of Gaza from Abbas's Fatah movement in a bloody 2007 coup, two years after Israel pulled its forces out of the territory it had captured in a 1967 war. (Writing by Allyn Fisher-Ilan; Editing by Sophie Hares)