Israeli tanks, helicopters and warplanes pounded a Hamas training camp yesterday, killing 14 militants in the deadliest attack in Gaza for nearly four months, as Israel struck back after a double suicide bombing.

A barrage of tank shells and missiles struck a militant training base in the town of Shijaia, a stronghold of Hamas, the Palestinian faction behind nearly simultaneous blasts that killed 16 people on two Israeli buses in Beersheba last Tuesday.

The 14 Palestinians killed in the strike were being trained by Hamas's military wing in guerrilla-tactics at a soccer field used at night as a training base for militants, locals said.

Gaza's main hospital was overwhelmed by casualties, many of them militants in camouflage with masks covering their faces. More than 20 people, including several bystanders, were injured, medical officials said.

"This ugly Israeli crime ... will not pass unpunished," Hamas spokesman Mushir al-Masri told Reuters. "It is an open war between the Zionists and us."

Hamas said all 14 dead were members of the militant group which is sworn to Israel's destruction.

The growing spiral of violence could further complicate Israeli Prime Minister Ariel Sharon's plan to withdraw troops and settlers from the occupied Gaza Strip by the end of 2005.

Militants are determined to claim any Israeli pullout as a victory, but the army has vowed to smash armed factions first.

Israeli leaders have pledged harsh reprisals, including the resumption of a campaign to assassinate Hamas leaders, in response to the Beersheba bombings, the first suicide attacks in the Jewish state in nearly six months.

Tanks stationed at the Nahal Oz border crossing between Israel and Gaza opened fire on Shijaia, a suburb of Gaza City, just after midnight (5 p.m. EDT) and warplanes and helicopters launched missiles, witnesses said.

The Israeli military said in a statement that it had "targeted a training field during training of Hamas terrorists."

It said Hamas members had been learning to make suicide belts, plant explosives, launch rockets, infiltrate Jewish settlements and kidnap soldiers and civilians.

"We will strike against Hamas wherever we can find it," Raanan Gissin, a spokesman for Sharon said.

"This is a relentless fight against terrorism."