GAZA CITY, Gaza Strip – Palestinian Arab terrorists blew up an Israeli army base at the Gaza-Egypt crossing yesterday by sneaking more than a ton of explosives through a tunnel, killing five Israeli soldiers, and wounding five in the largest Palestinian Arab attack in the month since Yasser Arafat’s death.

Hitting back, Israeli helicopters fired at least five missiles at targets in Gaza City early today, witnesses said. There were no reports of casualties. One missile started a fire at an abandoned metal workshop, while the other target was an empty house near the Islamic University, they said.

Also yesterday, imprisoned Palestinian Arab uprising leader Marwan Barghouti declared in a letter that he would throw his support to mainstream candidate Mahmoud Abbas in a January 9 election to replace Arafat, dropping out of the race. The move rids Mr. Abbas of his strongest rival and wards off what could have been a split in the leading Fatah faction of the PLO.

For his part, Mr. Abbas – who has stepped in as interim Palestinian leader until the elections – apologized to Kuwaitis for Palestinian support of Saddam Hussein during the 1990-1991 Gulf War – his latest gesture to mend fences with Arab nations offended by Arafat.

“Yes, we apologize for what we have done,” he said after arriving in Kuwait, responding to reporters’ questions about many Kuwaitis’ long-standing demands for an apology.

Arafat supported Iraq in its 1990 invasion of its tiny, oil-rich neighbor and opposed the subsequent American-led Gulf War that liberated it. He never visited Kuwait afterward.

In the violence along the Gaza-Egyptian border, the military said in a statement early today that five soldiers were killed and five were injured, including two seriously, in the explosion. The statement said two Palestinian Arabs charged the base and opened fire after the blast, and soldiers shot them dead.

Palestinian Arabs said one attacker was killed and the other escaped. The blast collapsed several structures at the crossing and damaged others.

The attack was another sign that the lull in violence after Arafat’s death on November 11 was over. On Tuesday, an Israeli soldier was killed in a blast at the entrance to another tunnel near the Gaza-Israel border, setting off Israeli retaliation that killed four Palestinian Arabs.

Palestinian Arab mortar and rocket barrages have hit Jewish settlements in Gaza daily, and terrorists have resumed firing homemade Qassam rockets at Israeli towns just outside Gaza. Israeli forces have returned fire, wounding several Palestinian Arabs.

Israeli army spokesman Captain Jacob Dallal said two explosions rocked the border terminal at Rafah.

“This was a very large, well coordinated, planned attack against an international crossing, used by Palestinian civilians to cross into Egypt,” Captain Dallal said, adding that the crossing would be closed until further notice.

Israel TV defense analyst Yoav Limor called the blast the result of an “intelligence failure.”

Palestinian Arabs in the area said they heard a loud explosion followed by machine gun fire. Palestinian Arabs said one gunman was killed in the exchange of fire, and a civilian was also killed. Unconfirmed reports said two Palestinian Arab suicide bombers were involved in the blasts.

A Palestinian Arab terrorist giving his name only as Abu Majad claimed responsibility in the name of the Fatah Hawks, an offshoot of the mainstream Fatah Party, and the terrorist group, Islamic Hamas.

A Hamas official, speaking on condition of anonymity, said 1.5 tons of explosives were set off in the blast, and a second, smaller explosive was detonated later. Masked Hamas terrorists said a gunman tried to kidnap a wounded soldier but killed him because the soldier resisted.

Hamas’s representative in Lebanon, Osama Hamdan, rejected calls for a halt to attacks on Israel and threatened new, unspecified types of retaliation against the Israeli occupation.

“The talk about a truce or a ceasefire is pure speculation and illusion. The (Israeli) enemy is still occupying our land. …The next few days will witness new lessons against the Zionist occupation,” Mr. Hamdan told about 2,000 Hamas supporters in Lebanon’s Ein el-Hilweh refugee camp on the outskirts of the southern port city of Sidon.

Abu Majad said the explosives-filled tunnel was 800 yards long. He said the attack was retaliation for what he called “the assassination” of Arafat, who died in a French hospital. Some Palestinian Arabs claim he was poisoned by Israel.

Raanan Gissin, a top aide to Prime Minister Sharon, told Associated Press Television News the attack could jeopardize efforts to normalize Israeli-Palestinian relations and restart peace moves after Arafat’s death.