The Palestinian interior ministry said on Tuesday there had been more than 30 Israeli air strikes on deserted militant training sites across Gaza.

The ministry said the targets included bases of Hamas and Islamic Jihad. There were no immediate reports of casualties.

According to the Israeli military, the airstrikes were a response to a barrage of 18 rockets fired into Israeli territory.

Tensions have risen in the West Bank and Gaza since the disappearance of Eyal Yifrah, 19, Gilad Shaar, 16, and Naftali Frankel, 16.

Their bodies were found in a field to the north of the city of Hebron on Monday, after the biggest ground operation by Israeli forces in the Palestinian territories in nearly a decade. The search operation involved house raids across the West Bank and was followed by the rocket attacks.

During the search, at least five Palestinians were killed and more than 400 arrested.

'Murdered in cold blood'

Israeli Prime Minister Benjamin Netanyahu said Hamas was to blame for the killings. Israel believes two alleged Hamas members, Marwan Qawasmeh and Amer Abu Aysha, are responsible for the murders, having abducted the three and shot them immediately afterwards.

"They were kidnapped and murdered in cold blood by human animals," he said. "Hamas is responsible and Hamas will pay," said Netanyahu.

Hamas itself has rejected the Israeli allegations, accusing Israel of using the teenagers' killings as a pretext for a military escalation against Palestinians.

"If the occupiers carry out an escalation or a war, they will open the gates of hell on themselves," Hamas spokesman Sami Abu Zuhri told the AFP news agency.

rc/lw (AFP, AP, dpa, Reuters)