Gaza City - Airstrikes and artillery fire by the Israel Defence Forces (IDF) directed at militants from the Palestinian Islamist movement Hamas in the Gaza Strip killed more than 120 people on Saturday and caused many more casualties, according to witness reports, medical and Israeli military sources.

The strikes targeted military facilities and fighters belonging to Hamas, Hamas and IDF sources confirmed.

Columns of black smoke could be seen rising from dozens of locations across the territory, and artillery fire was also reported against Palestinian militants firing rockets into Israel.

Hamas sources said that Tawfiq Jaber, chief of the movement's police organization in the territory, had been killed in the airstrikes, which had taken place within a few minutes on Saturday morning.

More than 30 of the movement's military installations had been bombed, the sources said.

A statement released by the IDF said that the targets attacked included "Hamas terror operatives that operated from the organization's headquarters, training camps and weaponry storage warehouses."

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 rules 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.

Witnesses also 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.

The IDF statement said that "the Hamas government leaders and operatives, which activate terror from within civilian population centres, are the sole bearers of responsibility for Israel's military response."

Civilian vehicles were helping ambulances in ferrying the wounded to Gaza's hospitals, and hospitals were urging civilians to donate blood, Palestinian medical sources said. (dpa)