Israel on Sunday continued intensive air strikes on the besieged Gaza Strip for the second successive day, killing 285 Palestinians so far in a powerful offensive aimed to halt nearly daily cross-border rocket attacks.

"The death toll so far is 285 and is subject to increase," said Mu'awia Hassanien, director of emergencies at the health ministry, adding that 900 have been wounded, 180 of them seriously.

Palestinians inspect a destroyed building of Hamas TV following an Israel air strike in Gaza Strip December 28, 2008. Israel launched air strikes on Gaza for a second successive day on Sunday. (Xinhua/Reuters Photo)

The latest Israeli strike hit the main security compound which houses the central prison, killing at least three prisoners and one of their guards.

Following the strike, the prisoners managed to flee the detention facility, though some Hamas militants tried to intercept them.

Israel launched the air strikes on the Gaza Strip before noon on Saturday, destroying more than 40 Hamas-linked security installations, including police stations, in a period of two minutes.

Israeli leaders said the offensive was in revenge for almost daily cross-border rocket and mortar fire from the Gaza Strip which intensified after a six-month truce between Gaza ruler Hamas and Israel expired a week ago.

Most of the fatalities were reported in the first air attacks in which F-16 fighter jets, Apache helicopters and drones were involved. The strikes continued throughout the night but less intensively.

Palestinian fire fighters extinguish a fire following an Israel air strike in Gaza Strip December 28, 2008. Israel launched air strikes on Gaza for a second successive day on Sunday, piling pressure on Hamas after 285 people were killed in one of the bloodiest 24 hours for Palestinians in 60 years of conflict with the Jewish state.(Xinhua/Reuters Photo)

Al-Aqsa satellite channel, run by Hamas, was among the targets that the fighter jets attacked after midnight and its four-story building were completely destroyed. Minutes later, the channel resumed broadcast from unknown studios prepared in advance as an alternative.

Palestinian militants responded by firing rockets into Israel since the first hour of the offensive. Gaza militants fired some 80 rockets into the Jewish state, according to emergency service.

On Sunday morning, Hamas operatives launched three Grads (military-grade rockets) towards Israel, which landed near main port Ashdod, Israeli news service Ynet reported, adding it marked the northernmost range of Gazan rockets seen to date-- more than 40 km.

Israel Defense Forces (IDF) sources, however, said Hamas response so far to Israel's aerial attack of strategic targets in Gaza was relatively restrained, despite the rocket fire of short-range and Grads, adding that it is possible for Hamas to give a massive response.

It was far too early to assume Hamas has been subdued, said the IDF, noting that the militant group still has the capacity to shoot heavy barrages of rockets, as well as to attempt terror attacks along the fence between Gaza and Israel, and in Israel itself.

Streets in Gaza were empty except for the ambulance and fire engine trucks as the Palestinian National Authority (PNA), based in West Bank, and the deposed Hamas administration in Gaza announced a three-day mourning.

"It is like an earthquake," said Gaza resident Mohammed Jafarawi in his description of the situation.

"The earthquake kills most of the people in a matter of few minutes and then more people die in the subsequent shakes," he said, referring to the first simultaneous strikes.

Editor: Yan