Israeli airstrikes have killed seven Islamic Jihad fighters in the Gaza Strip, prompting a massive barrage of retaliatory rocket fire, officials have said.

Adham Abu Selmiya, a spokesman for Gaza’s emergency services, said on Saturday that five members of the Al-Quds Brigades, Islamic Jihad’s armed wing, were killed and three wounded in a first Israeli attack on their camp.

As fighting continued into the night, Israeli aircraft struck four more targets in Gaza, witnesses and Palestinian officials said, killing two fighters and wounding two others allegedly preparing to fire a missile near Rafah, in the south of the strip.

An Israeli strike east of Gaza City and two in the area of Khan Yunis, in the south, caused no casualties, witnesses said.

As rockets and mortar shells were fired into Israel, police said they were raising their national alert to its second-highest level.

The Israeli military said the Rafah raid "targeted a terrorist squad in the southern Gaza strip responsible for the firing of military-use projectiles towards the Israeli home front".

The Al-Quds Brigades confirmed that five members, including a commander named as Ahmed al-Sheikh Khalil, were killed in the first strike on their training camp near Rafah.

The strikes were the bloodiest since a tacit ceasefire was agreed between Palestinian fighters and Israel in late August.

"There is no chance of speaking about a truce now, following such a big crime against leaders of the group," Abu Ahmed, an Islamic Jihad spokesman, said.

He added: "Now we are talking about the suitable response to this crime".

Within hours, at least 20 Palestinian rockets and mortar bombs hit different sites in southern Israel, wounding three civilians, police said.

One rocket slammed into a community centre and another into a block of flats, setting parked cars and gas canisters alight.

Rockets hit the city of Ashdod, the nearby town of Gan Yavneh and the city of Ashkelon, to the south, police said.

A statement from the Al-Quds Brigades claimed responsibility for the rocket fire and posted a video on its website which it said showed the launching of five of the rockets.

A spokesman for Hamas’ Ezzedine al-Qassam Brigades said other armed groups were mulling their response.

"The occupation is completely responsible for the crime in Rafah and all of the resistance factions cannot leave the shedding of our martyrs’ blood unanswered," Abu Obeida, a spokesman for Hamas, said.

"We shall discuss the answer to this crime."

Islamic Jihad, a sometime ally of Gaza’s ruling Hamas, has expressed frustration over recent efforts by the more powerful faction to impose ceasefires with Israel.

The air raid and earlier rocket attack were the first violent incidents since October 18 when Hamas repatriated Gilad Shalit, an Israeli soldier it seized in 2006, in exchange for the release of more than 1,000 jailed Palestinians.
 
(Agencies via Al Jazeera)