Gaza City - At least 100 Gazans have been killed in Israeli bombardment on Tuesday, Gaza officials have said, hours after shells hit the enclave's only power station.

A thick column of black smoke was seen rising from the power station on Tuesday, mingling with other plumes sent into the air by Israeli shelling.

Gaza officials said the death toll from the invasion had now reached 1,178, with at least 100 killed since midnight on Tuesday. More than 6,800 Gazans had been injured. The AFP news agency reported that one air raid alone in northern Gaza had killed 10 people on Tuesday.

Bombs hit the power station's generator.

Jamal Dardasawi, a spokesman for the electricity distribution company, warned that Gaza would be engulfed in "a humanitarian crisis within hours" if no immediate action was taken to secure power supplies.

"This will affect hospitals and water. All aspects of life are endangered," Dardasawi said.

Rafiq Maliha, the director of the power station, told Al Jazeera that two turbines were directly hit, adding that the plant would not be operational for up to a year.

At full capacity, the station provided Gaza with 80mw of electricity but had been generating only 50-60mw before it was bombed. The lines to outside power sources provided an additional 120mw of electricity, Dardawasi said.

"This amount of power can't be distributed technically into other parts of Gaza and it's not even enough for Rafah city," he said.

"Today, all Gaza Strip is without power, we can't talk about percentages."

Gaza also relies on power lines from Israel and Egypt to meet its energy needs. Dardasawi said eight of the 10 lines from Israel had been damaged since Israel invaded Gaza.

With the facility now shut down and most power lines from Israel severed, Palestinians in Gaza will be forced to depend on electricity bought from neighbouring Egypt.

Said al-Soudi, the head of Gaza's civil defence ministry, said technical crews had succeeded in putting out a fire at the station.

He told Al Jazeera that he received an emergency call about the shelling at 5.30am, but only reached the facility three hours later, after securing safe passage to the site through the Red Cross.

"Despite the coordination, shells were still landing," he said.