KFAR CHOUBA, Lebanon (AP) _ Israel _ still engaged in violence with the Palestinians _ faced fresh security problems Sunday in Lebanon, where it rained missiles and machine gun fire in retaliation for a Hezbollah bombing that killed one soldier.

The assault was Israel's first cross-border retaliatory attack since pulling its troops from southern Lebanon in May to end Israel's 18-year occupation of a border enclave there. The Israeli army confirmed striking back with gunfire after the roadside bombing in Chebaa Farms near the Lebanese border. One civilian was slightly injured on the Lebanese side.

Lebanese President Emile Lahoud, in comments on state-run television, called the Israeli raids a ``grave precedent that may entail serious repercussions for which Israel is alone responsible.''

The violence at Chebaa Farms _ an uninhabited strip of land in the western foothills of Mount Hermon where the borders of Lebanon, Syria and Israel meet _ occurred against the backdrop of continued Israeli-Palestinian clashes.

On Sunday, Israeli soldiers killed four armed Palestinians as they set out from the Palestinian West Bank city of Qalqilya into an area under Israeli control, an Israeli army spokesman said. The Palestinians had opened fire a short time earlier on an Israeli car driving to a nearby Jewish settlement, the spokesman said.

Israeli soldiers also returned fire from Palestinian gunmen Sunday in the West Bank city of Hebron, the southern Gaza Strip and the southern edge of Jerusalem. The only fatality was a Palestinian who died in the Gaza Strip from head wounds suffered in a clash six days earlier, Palestinian doctors said.

Two months of fighting in the West Bank and Gaza have left more than 270 people dead, most of them Palestinians.

Israeli Prime Minister Ehud Barak acknowledged Sunday on Israeli radio that ``never has an Israeli government used such great force against the Palestinians _ rockets, tanks, and returning fire when needed.''

Barak, who was a general before becoming a politician, assured Israelis that he knew how to handle the conflict. He said he was pursuing diplomatic efforts to salvage seven years of peacemaking with the Palestinians.

Foreign Minister Shlomo Ben-Ami, who was tentatively scheduled to travel Monday to Russia for talks on the Mideast crisis, said Sunday that Arafat has been sending signals in the past few days saying he wants to end the violence. ``We have an interest in putting these signals to the test,'' Ben-Ami told Israeli Channel 1 television.

The attacks in south Lebanon also came a day before the start of Ramadan, the holiest month in the Islamic calendar. Two Arab countries, Egypt and Jordan, took the unusual step of using the Muslim holiday to call for the ``liberation'' of a revered Jerusalem mosque from Israeli control.

The al-Aqsa Mosque, part of a compound in east Jerusalem that Israeli troops captured in 1967, is the third-holiest shrine in the Muslim world.

The Hezbollah, in a statement issued in Beirut, said the guerrilla attack Sunday was part of ``its duty to complete the liberation of the occupied territory.'' The Iranian-backed Shiite Muslim militant group, which led the guerrilla war against Israel in south Lebanon, has vowed to continue fighting as long as Chebaa Farms remain under Israeli control.

Israeli soldiers patrolling the area found the bomb shortly after 6:30 a.m. about two-thirds of a mile inside the Israeli-occupied Golan Heights, Israeli Brig. Gen. Moshe Kaplinsky said Sunday.

Guerrillas detonated it as a tracker and another soldier were examining the explosive from a distance, killing the Bedouin tracker, Kaplinsky told Israeli radio. The tracker was identified as Sgt. Maj. Khalil Taher.

Soon after, two Israeli fighter jets fired six missiles at suspected guerrilla hide-outs in the hills near the village of Kfar Chouba, about a mile from Chebaa Farms, Lebanese security officials said. Helicopter gunships also fired missiles and machine guns, they said.

In Jerusalem, the Israeli army confirmed that warplanes attacked Hezbollah targets in Lebanon.

``We did all we think we could do for a swift conclusion of the incident,'' Kaplinsky said. ``We will continue to do all we think we need to.''

Flying debris from a missile struck a Syrian laborer in the leg as he worked on a road at the northeastern entrance to Kfar Chouba, slightly injuring him.

In Beirut, Rolf Knutsson, U.N. Secretary-General Kofi Annan's representative for southern Lebanon, said the roadside bombing and ensuing hostilities ``are cause for serious concern.''

``This is yet another grave incident underscoring the urgent need to ensure full respect for the withdrawal line, on the ground as well as in the air,'' Knutsson said.

An Israeli patrol in disputed Chebaa Farms was the target of a previous Hezbollah bomb that injured two soldiers on Nov. 16. Hezbollah guerrillas also ambushed a patrol in the area on Oct. 7, seizing three Israeli soldiers and offering to free them in exchange for Arabs being held in Israeli prisons.

Lebanon and Syria consider Chebaa Farms Lebanese. Israel and the United Nations say it lies behind a U.N.-drawn border line recognized by Lebanon and Israel and is part of the Golan Heights, which Israel captured from Syria in the 1967 Mideast war and annexed in 1981.