Lebanese Prime Minister Fouad Siniora has described an Israeli commando raid against Hizbollah as a “naked violation” of the current truce.
Three Hizbollah fighters and one Israeli soldier died in the clash near Bodai, 26 kilometres from the Syrian border.
The Israelis said they had to act to stop arms being delivered to the guerrillas.
“We had specific information of a weapons shipment from Syria for Hizbollah,” said Israeli spokesman Mark Regev.
“That is a direct violation of the UN Security Council resolution that established the ceasefire and we were responding to that violation of the ceasefire.”
Both Syria and Iran deny accusations they supply arms to Hizbollah.
One Lebanese politician, who is allied to the guerrilla group, claimed the Israelis had launched the assault in order to provoke Hizbollah into retaliation and disrupt the deployment of the Lebanese army in the south of the country.