Hezbollah guerrillas fought a deadly battle with Syrian rebels in Lebanon's eastern border region.
Sources said at least 12 rebels were killed and one Hezbollah fighter in the fighting east of the Bekaa Valley town of Baalbek.
The toll will not be clear until bodies are retrieved from the remote and rugged border area.
Syria's two-year-old conflict has increasingly sucked in its smaller neighbour.
Other incidents include deadly fighting shaking the northern Lebanese city of Tripoli and rockets hitting the Bekaa Valley and southern Beirut.
Eariler, Syria said it will allow the Red Cross to enter the besieged town of Qusair after military operations are over.
Foreign Minister Walid al-Moualem made the pledge to UN Secretary General Ban Ki-moon this afternoon, state TV said.
UN humanitarian officials have called for an immediate ceasefire in Qusair, where President Bashar al-Assad's forces and Hezbollah fighters are battling to drive out rebels.
The UN says 1,500 wounded people are in need of emergency medical treatment.
Russia last night blocked a UN Security Council declaration of alarm over the siege Qusair, diplomats said.
Qusair, near the Syrian-Lebanese border, is usually home to an estimated 30,000 people.
Fighting for control of the town has raged for two weeks.
Council statements must be agreed unanimously.
Russia blocked the draft text, saying it was "not advisable to speak out as the UN Security Council didn't when Qusair was taken by the opposition," a council diplomat said on condition of anonymity.