Beirut, Lebanon - Israeli commandos raided a Hezbollah stronghold deep in Lebanon on Saturday, engaging in a fierce gunbattle, and the Lebanese government threatened to halt further troop deployments in protest as the 6-day-old UN-brokered ceasefire was put to a critical test. Secretary-General Kofi Annan called the operation a violation of the UN truce, according to a statement from his spokesman.

Israel said the raid, launched to stop arms smuggling from Iran and Syria to the militant Shiite fighters, left one Israeli officer dead and two soldiers wounded.

There were no signs of further clashes, but the flare-up underlined worries about the fragility of the ceasefire as the UN pleaded for nations to send troops to an international force in southern Lebanon that is to separate Israeli and Hezbollah fighters.

A contingent of 49 French soldiers landed in the south Saturday, providing the first reinforcements for the 2,000-strong UN peacekeeping mission known as UNIFIL that has been stationed in the region for years. About 200 more were expected next week.

They were the first additions to what is intended to grow into a 15,000-soldier UN force to police the truce with an equal number of Lebanese soldiers. France leads UNIFIL and already had 200 soldiers in Lebanon before the reinforcements.

But with Europe moving slowly to provide more troops, Israel warned it would continue to act on its own to enforce an arms embargo on the Lebanese guerrilla group until the Lebanese army and an expanded UN peacekeeping force are in place.

"If the Syrians and Iran continue to arm Hezbollah in violation of the resolution, Israel is entitled to act to defend the principle of the arms embargo," Israeli Foreign Ministry spokesman Mark Regev said. "Once the Lebanese army and the international forces are active ... then such Israeli activity will become superfluous."

Defense Minister Elias Murr met with UN envoy Terje Roed-Larsen and threatened to halt the movement of Lebanese troops into the former war zone in the south if the United Nations did not intervene against Israel. That could deeply damage efforts to deploy a strong UN peacekeeping force.

"We have put the matter forward in a serious manner and the UN delegation was understanding of the seriousness of the situation," Murr told reporters. "We are awaiting an answer."

Israeli Prime Minister Ehud Olmert defended the raid during a phone conversation with UN Secretary-General Kofi Annan, saying it was "intended to prevent the re-supply of new weapons and ammunition for Hezbollah," officials said, speaking on condition of anonymity because they weren't authorized to speak publicly on the issue.

The Israeli leader pointed to the importance of the supervision of the Syrian-Lebanese border as well, they said.

The Israeli military also said the raid was launched "to prevent and interfere with terror activity against Israel, especially the smuggling of arms from Iran and Syria to Hezbollah."

The Foreign Ministry spokesman rejected the characterization of the raid as a truce violation, saying the Lebanese army and UN peacekeepers must take control of Lebanon's border with Syria to ensure arms don't reach Hezbollah.

"But in the interim, of course, we can't have a situation where endless amounts of weaponry arrive for Hezbollah, so we are forced to act in response to this violation," he said, warning that further incursions could occur.

A statement issued by Annan's spokesman later Saturday said that the UN chief spoke with both Lebanese Prime Minister Fuad Saniora and Olmert about the fighting. "The secretary-general is deeply concerned about a violation by the Israeli side of the cessation of hostilities," it said.

"All such violations of Security Council Resolution 1701 endanger the fragile calm that was reached after much negotiation," said the statement, issued by spokesman Stephane Dujarric.

The White House declined to criticize the raid, noting that Israel said it acted in reaction to arms smuggling into Lebanon and that the UN resolution calls for the prevention of resupplying Hezbollah with weapons.

"The incident underscores the importance of quickly deploying the enhanced UNIFIL," White House spokeswoman Jeanie Mamo said.

Roed-Larsen said earlier the Lebanese army has deployed more than 1,500 soldiers in three sectors of the south where Israeli forces have left, and the 2,000 peacekeepers of UNIFIL have set up checkpoints and started patrolling the areas.

The broad outlines of the UN ceasefire plan call on Hezbollah to halt all attacks and for Israel to stop offensive operations. It gives Israel the right to respond if attacked, but the commandos were flown in by helicopter and the raid took place far from Israeli troops in southern Lebanon.

Israel did not identify the officer killed in the raid. Hezbollah issued a terse statement saying guerrillas "ambushed" the commando force and suffered no casualties. Lebanese security officials said three guerrillas were killed and three wounded.

The security officials said the commandos flew in by helicopter to a hill outside the village of Boudai west of Baalbek in eastern Lebanon, about 17 miles from the Syrian border. Witnesses said Israeli missiles destroyed a bridge during the fighting.

The officials, who spoke on condition of anonymity because they were not authorized to release information to the media, said the Israelis apparently were seeking a guerrilla target in a nearby school but they had no other details.

Lebanese media speculated that Sheik Mohammed Yazbeck, a senior Hezbollah official in the Bekaa Valley and a member of the group's executive council, may have been the target. Yazbeck is a native of Boudai.

The Israeli army denied it had captured any Hezbollah fighter, and said it had not been the raid's objective.

Overflights by Israeli jet fighters drowned out the clatter of helicopters that flew the commandos into the foothills of the central Lebanese mountains, local Hezbollah officials said.

Using two vehicles also delivered by helicopter, the commandos drove into Boudai and were intercepted by Hezbollah fighters in a field, the officials said. They said the Israelis identified themselves as Lebanese soldiers, but the guerrillas grew suspicious and gunfire erupted.

Israeli helicopters fired missiles as the commandos withdrew and flew them out of the area an hour later, the Hezbollah officials said.

Witnesses reported seeing bandages and syringes at the landing site outside Boudai. The bridge that witnesses said was destroyed was about 500 yards from the landing site.

The area in the eastern Bekaa Valley, 60 miles north of the Israeli border, is a major guerrilla stronghold. Baalbek is the birthplace of Hezbollah, a militant Islamic movement that is supported by Iran and Syria.

Hezbollah, meanwhile, buried 55 fighters Friday and Saturday in Haris, Majdel Silim, Bint Jbail, Deir Qanoun and south Beirut, security officials said. Israel claims it killed hundreds of guerrillas during the war. Hezbollah reported 68 deaths.

UN Deputy Secretary-General Mark Malloch Brown said more countries needed to join the peacekeeping force. The UN wants to have 3,500 soldiers on the ground by Aug. 28 to help police the truce that took effect Monday and ended 34 days of brutal warfare.

Bangladesh, Indonesia, Italy, France and Finland have promised troops. In an effort to encourage more countries to sign on, Annan said the peacekeeping force would not "wage war" on Israel, Lebanon or Hezbollah militants, addressing a key concern of many countries.

The UN and Lebanon's government have said Hezbollah will not be allowed to bring weapons out in public, but have declined to commit to trying to disarm the guerrillas, as called for in a September 2004 UN resolution.