Gaza City:  Three Palestinians, including a schoolboy, were killed on Sunday, raising the death toll from Israeli air strikes on Gaza to 18 in less than 48 hours, medics said.
   
The latest raid hit an area northeast of Gaza City, killing a 60-year-old man who medics said was a civilian, several hours after a strike slightly further north killed a 12-year-old boy in Jabaliya refugee camp.
   
The spike in violence erupted on Friday afternoon when an Israeli strike killed the leader of the Popular Resistance Committees (PRC).
   
It sparked a bloody cross-border exchange in which 15 Gazans were killed and more than 100 rockets fired at Israel on Friday and on Saturday, marking the deadliest 24-hour period in the border area in more than three years.
   
Since then, three more people have been killed, raising the toll to 18, including 15 militants, medics said. At least 30 people were wounded, six of whom were in critical condition.
   
The European Union and United States have urged both sides to restore calm. But Palestinian militants vowed to avenge their dead and Israel threatened to hit back if its citizens came under renewed rocket attacks from the coastal enclave.
   
Since midnight, Israel staged at least four strikes, one of which killed a man in Zeitun in eastern Gaza City, and a second which killed 12-year-old Ayub Asaliya who was on his way to school in Jabaliya refugee camp.
   
His seven-year-old brother was moderately wounded, medics said. Another strike in eastern Gaza City injured one person before the 60-year-old was killed northeast of the city.

(Agencies)