Two Israeli tank shells have hit a fuel tank at the Gaza Strip's only power plant, a spokesman for Gaza's electricity distribution company said today.
A huge cloud of black smoke was seen rising above Gaza City after the explosion.
Power company spokesman Jamal Dardasawi said the shells hit one of three tanks in the plant compound which currently store fuel.
There was no immediate word of casualties.
Even before the strike, Gaza residents had electricity for only about three hours a day. The strike is bound to reduce supplies even further.
The Israeli military had no immediate comment.
Earlier, at least two major explosions hit a media complex in central Gaza City housing the offices of Al Aqsa television and radio. The building also houses offices of a number of Arab satellite television news channels.
A loud explosion was also heard within the Abu Khadra government complex in the coastal city.
The strikes came during a heavy night of bombardment, with Israeli illumination flares and repeated explosions lighting up the Gaza skyline and turning it orange.
The hit on the power plant came as Israeli aircraft and tanks struck symbols of Hamas control in Gaza overnight and into today, their heaviest bombardment of the densely populated coastal territory since the war between Israel and the Islamic militants began more than three weeks ago.
The pounding came just hours after Israeli Prime Minister Benjamin Netanyahu warned in a televised speech of a "prolonged" campaign in Gaza.
Hamas also signalled defiance. Ismail Haniyeh, the Hamas leader whose house was struck in an air strike early today, said in a statement that "destroying stones will not break our determination".
The tough words by both sides came amid mounting international appeals for an unconditional ceasefire.
However, Hamas has said it will not stop fighting until it wins international guarantees that a seven-year-old border blockade of Gaza will be lifted. I
Israel said its troops will not leave Gaza until they have demolished several dozen Hamas military tunnels under the Gaza-Israel border.
Late yesterday, Mr Netanyahu signalled that Israel is intensifying its air and ground campaign.
The overall Gaza death toll rose to at least 1,110, according to Gaza's Health Ministry. Israel says it has lost 53 soldiers, along with two civilians and a Thai worker.