Israeli civilians were ordered into bomb shelters for an hour Sunday during attacks along the Lebanese border that injured six Israeli soldiers.

Israeli Prime Minister Ariel Sharon said the clashes "could perhaps lead to a very big outbreak" as Israel responded with tanks, artillery and airstrikes. Lebanese witnesses said Hezbollah guerrillas fired a shoulder-launched missile at an Israeli jet.

The fighting has raised fears of a new front opening up in the Mideast conflict, as Israel presses its military offensive in Palestinian cities.

The Israeli military chief of staff, Lt. Gen. Shaul Mofaz, warned that Israel is prepared to hit back at "the centers of power" in Lebanon. "When red lines are crossed, we will know how to act," he said.

In a phone conversation late Sunday, Israeli Foreign Minister Shimon Peres asked U.S. Secretary of State Colin Powell to intervene with Lebanon and Syria to calm the border, according to a statement from Peres' office.

Guerrillas opened fire on several Israeli villages and army bases from Lebanon, the military said in Jerusalem. Four women soldiers were injured, one seriously, at an army post next to the village of Avivim, rescue workers said.

In other attacks, rifle fire was aimed at an army position near Kibbutz Manara, a collective farming community in the Galilee panhandle, a strip of Israeli territory bordering Lebanon. No injuries were reported on the Israeli side and troops returned fire, the army said.

Also, rockets were fired at Israeli military posts in the Golan Heights, near the Lebanon border. Two soldiers were injured, an army statement said.

A Hezbollah statement issued in Beirut said the group's fighters targeted six Israeli military outposts in "fierce confrontations" in the Chebaa Farms area. It said the guerrillas "scored direct hits."

Israel retaliated with tank and artillery fire, the Israeli military said.

Lebanese security officials said Israeli gunners fired around 30 artillery shells and that Israeli jets also fired at least four missiles in several sorties.

Witnesses said guerrillas fired at least one shoulder-launched missile at an Israeli jet, but missed. Though the shoulder-fired missiles have been used in the past, it was the first time Hezbollah guerrillas fired at jets in recent days.

Lebanon and Syria say Chebaa Farms is Lebanese while the United Nations says it belongs to Syria. Israeli troops withdrew from southern Lebanon in May 2000 after an 18-year occupation.

On Saturday, Israeli forces launched artillery and air attacks on areas in southern Lebanon in response to an attack on the village of Ghajar in the Golan Heights.

Armed men drove in a car close to the Lebanese border and fired five mortar rounds on an Israeli post near Ghajar, then fled. It was not clear who was behind the attack.

One mortar hit a home on the Israeli side, injuring three children ages 3, 6 and 15.