Lebanon's defence minister has warned that any group breaking the ceasefire with Israel would be "decisively dealt with" and considered a traitor.
And the Lebanese prime minister Fuad Siniora, standing in the rubble of south Beirut, said the Israeli bombing campaign was a "crime against humanity".
The strong words from Defence Minister Elias Murr last night indicated concern that factions other than Hezbollah, which he said was committed to the ceasefire, might try to draw retaliation from Israel by firing on the Jewish state.
"We consider that when the resistance (Hezbollah) is committed not to fire rockets, then any rocket that is fired from the Lebanese territory would be considered collaboration with Israel to provide a pretext [to Israel] to strike," he told a news conference at the Defence Ministry.
On Saturday, Murr threatened to stop the deployment of the army in south Lebanon, a key demand of the UN cease-fire resolution, after Israel's helicopter-borne commando raid deep in the Bekaa Valley. Israel said it launched the raid to intercept weapons shipments for Hezbollah from Syria. One Israeli officer was killed and two soldiers were wounded, one seriously.
Lebanon was in the process of sending 15,000 soldiers to the south, putting a government force in the region for the first time in four decades, as part of the ceasefire requirements. It was to be joined by an equal force of international peacekeepers, but wrangling among countries expected to send troops has so far delayed assembly of the force.
UN Secretary General Kofi Annan declared the raid a violation of the ceasefire.
Murr's concern arose from the past practice Palestinian radical guerrilla groups backed by Syria have of firing rockets on Israel but on a much smaller scale than the Hezbollah barrage during the 34-day war.
Lebanese Prime Minister Fuad Siniora made a tour of south Beirut, surrounded by a mob of reporters and television crew. He was accompanied by Parliament Speaker Nabih Berri, a Hezbollah supporter, who said the two leaders spoke with one voice. He then stood aside as Siniora issued an impassioned statement.
"What we see today is an image of the crimes Israel has committed... there is no other description other than a criminal act that shows Israel's hatred to destroy Lebanon and its unity," he said.
"I hope the international media transmits this picture to every person in the world so that it shows this criminal act, this crime against humanity that Israel has committed," the Western-backed prime minister said.
Israel said its raid in the Bekaa Valley was launched to stop arms smuggling from Iran and Syria to the militant Shiite fighters. There have been no repeated raids since the attack early yesterday, and Hezbollah did not retaliate. Nevertheless, the flare-up underlined concern about the fragility of the ceasefire as the UN pleaded for nations to send troops to an international force in southern Lebanon.
A contingent of 49 French soldiers landed in the south on 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. 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."
A statement issued by Kofi Annan's spokesman said the UN chief spoke with both Siniora and Olmert about the fighting.