MAJIDIYA, Lebanon (AFP) - Two Israeli soldiers and a Spanish UN peacekeeper were killed on Wednesday as Lebanon's Hizbollah and Israel exchanged fire in their most serious clashes in years.

The violence raised fears of another full-blown conflict erupting between the bitter enemies, who fought a month-long war in 2006.

The two soldiers were killed when Hizbollah fired an anti-tank missile at a military convoy in an Israel-occupied border area, the army said.

Seven other soldiers were wounded but local media said none had suffered life-threatening injuries.

Israel responded with "combined aerial and ground strikes" on southern Lebanon after the attack - an apparent retaliation for a recent Israeli strike on the Golan Heights that killed senior Hizbollah members.

Lebanese security sources told AFP that Israeli forces had hit several villages along the border.

Clouds of smoke could be seen rising from Majidiya village, one of the hardest hit. There was no immediate information on casualties.

A 36-year-old Spanish corporal from the UN peacekeeping force in southern Lebanon was killed in the exchange of fire, officials said.

The 10,000-strong UNIFIL mission said it had observed six rockets fired towards Israel from southern Lebanon and that Israeli forces "returned artillery fire in the same general area".

It said the precise cause of the peacekeeper's death was "as yet undetermined" and urged all sides to show "maximum restraint to prevent an escalation".

Hizbollah said it had targeted an Israeli military convoy "transporting several Zionist soldiers and officers".

'VERY HARSH' RESPONSE

"There were several casualties in the enemy's ranks," Hezbollah said in a statement broadcast on the Shi'ite militant group's Al-Manar television channel.

Israel said that mortar fire was also aimed across the border at several military facilities but that no one was hurt.

Israeli military leaders convened to discuss their response as Prime Minister Benjamin Netanyahu warned that the army was "ready to act with force on any front".

On a visit to China, hardline Foreign Minister Avigdor Lieberman said on Twitter that Israel should respond to the attack "in a very harsh and disproportionate manner, as China or the US would respond to similar incidents."

Army spokesman Brigadier-General Moti Almoz warned that Israel was considering further action.

"This is not necessarily the last response," he wrote on Twitter.

Hizbollah's attack was hailed by the Palestinian Islamist groups Hamas and Islamic Jihad.

"We affirm Hezbollah's right to respond to the Israeli occupation," Hamas spokesman Sami Abu Zuhri said, while Jihad's Quds Brigade praised the attack as "heroic".

Israeli security sources said at least one house in the divided village of Ghajar - which lies partly in Israel and partly in Lebanon - had been hit.

All roads to the village were blocked off by Israeli police, with a crowd of villagers anxiously waiting to get home to check on their families.

"Three houses were hit by rockets," said Mr Hussein, 31, relaying what he had heard by telephone from relatives in the village of 2,000 inhabitants.

He said a number of villagers had been wounded but did not know how badly.

Other frantic family members argued with police to be allowed in to collect their children, who had been locked inside the village school for their own safety.

BUILDING TENSIONS

Tension in the area had been building, especially after an Israeli air strike on the Syrian sector of the Golan Heights killed six Hizbollah fighters and an Iranian general on Jan 18.

The day before the raid, Hizbollah leader Hassan Nasrallah threatened to retaliate against Israel for its repeated strikes on targets in Syria and boasted the Shi'ite militant movement was stronger than ever.

Israeli warplanes also struck Syrian army targets in the Golan Heights early on Wednesday, hours after rockets hit the Israeli-held sector.

Defence Minister Moshe Yaalon said Israel would not tolerate any attacks.

"We will not put up with any fire at Israeli territory or any breach of our sovereignty, and we will respond with force and determination," he said in a statement.

In 2006, Israel fought a war against Hezbollah that killed more than 1,200 people in Lebanon, mostly civilians, and some 160 Israelis, mostly soldiers.

Israel occupied parts of Lebanon for 22 years until 2000 and the two countries are still technically at war.

Wednesday's missile attack was on Israeli forces in the Shebaa Farms area, a mountainous, narrow sliver of land occupied by Israel since 1967.