The Lebanese Prime Minister, Fouad Siniora, has described an Israeli commando raid in Lebanon as a naked violation of the UN-brokered ceasefire.
It is understood that one Israeli soldier and three Hezbollah fighters were killed in the operation in the Bekaa Valley - the first big attack since the truce came into force five days ago.
The Israeli army said the raid, which involved aircraft and commandos, was aimed at disrupting the shipment of weapons to Hezbollah from Syria and Iran.
Mr Siniora has said he has passed on his condemnation of the incident to UN envoys who are visiting Lebanon.
Lebanese Defence Minister Elias al-Murr said he might seek to halt the deployment of troops to the south if the UN did not clarify its position on the raid.
Meanwhile, a group of French peacekeepers have reached the UN's main base in Lebanon.
The 49 military engineers, who sailed into the port of Naqoura, are the first contingent of the 200 army engineers promised by France.
Israel has expressed concern that some of the troops due to be sent to southern Lebanon will be from countries that do not recognise Israel's right to exist.
But UN spokesman Edward Mortimer said that the issue should not be a sticking point.
Last night, the UN Secretary General, Kofi Annan, made a strong appeal to member states to provide troops for a peacekeeping force in Lebanon.
Mr Annan warned that the situation on the ground was still fragile five days after a ceasefire came into force.
He urged Israel to lift its air and sea blockade on Lebanon so aid could be delivered quickly.
