Gaza City - Surprise airstrikes and artillery fire by the Israeli military directed at Palestinian militants in the Gaza Strip caused dozens of casualties on Friday, according to witness reports and medical sources.

Columns of black smoke could be seen rising from at least 10 locations across the territory on Saturday, and artillery fire was reported against Palestinian militants firing rockets into Israel.

Medical sources said in initial reports that at least 10 people had been killed in the airstrikes.

Arabic television station al- Jazeera broadcast pictures showing the motionless bodies of a number of young men lying on the ground in Gaza.

Airstrikes also paralysed the mobile telecommunications network in the territory.

The attacks, although an expected response to a wave of rocket fire by the military associates of the Islamist Hamas movement that has ruled Gaza since the end of a ceasefire on December 19, came as a surprise on Saturday, as previous Israeli media reports had not expected a decision to strike before Sunday.

Palestinian security sources told Deutsche Presse-Agentur dpa that the airstrikes targeted police and security installations run by the Hamas movement.

Witnesses said that Israeli artillery fire struck at Palestinian militants who had fired rockets into Israel west of the town of Beit Lahiya, in the north of the Gaza Strip.

Three members of Hamas' military wing were injured by shrapnel, Palestinian emergency official Mu'awia Hassanien said.

According to Israeli army reports, since the end of the ceasefire, Palestinian militants have fired some 180 rockets and mortar rounds into Israeli towns and villages bordering Gaza, although with few casualties. (dpa)