Nahal Oz, Israel: Palestinian fighters on Wednesday attacked an Israeli-controlled border post where fuel is piped into the Gaza Strip, killing two Israeli civilians, the Israeli army said.

Two Palestinian fighters and two civilians - including a boy - were killed when Israeli tank shells struck a building near the Nahal Oz terminal, Palestinian medics said. Another fighter died in an air strike in Gaza City.

Hours earlier, an Israeli soldier and a Hamas fighter were killed in clashes in southern Gaza, both sides said. Yesterday's death toll was the highest in the territory since Israel waged a ground sweep that killed scores of Palestinians in March.

Hamas had warned on Tuesday of an "explosion" in the territory if Israel continued its economic blockade. Israel tightened its cordon after Hamas Islamists violently took over the Gaza Strip in June.

Fighters from three movements, not including Hamas, infiltrated the Nahal Oz crossing, said a spokesman for one of the groups, the Popular Resistance Committees (PRC), describing the operation as an attempt to abduct soldiers.

Hamas's armed wing said it pounded the area with mortar bombs and heavy machinegun fire during the operation, which the PRC dubbed "Breaking Zionist Arrogance".

In addition to the PRC, Islamic Jihad and the Mujahideen Brigades, which is affiliated with President Mahmoud Abbas's Fatah faction, claimed responsibility for raiding Nahal Oz.

"The target was a Zionist army base and the aim was to abduct soldiers to swap them for Palestinian prisoners," said the PRC spokesman, Abu Mujahed.

Mark Regev, a spokesman for Israeli Prime Minister Ehud Olmert, said the attack on a fuel terminal that supplies Gaza with its energy needs "shows the blatant disregard the terrorists [fighters] have for the well-being of the people of Gaza". All the fuel pumped into the Gaza Strip passes through Nahal Oz.