A mortar shell fired from inside a besieged Palestinian refugee camp struck a Red Cross vehicle, killing two of the aid agency's workers and critically injuring a third, Lebanon's state-run news agency and security officials said.
The violence came as the UN Security Council gave strong backing to the Lebanese government's fight against militants.
The National News Agency said the two local aid workers were killed near the northern edge of Nahr el-Bared camp by shelling from Fatah Islam militants holed up inside. A security official said later in the day that troops had destroyed the residence and headquarters of the militant group's leader.
Other security officials said the workers were killed when their vehicle was struck by what appears to be a mortar shell fired from inside the camp. A third Red Cross worker was seriously wounded.
The security officials, who spoke on condition of anonymity because they were not allowed to give official statements to the press, said there were army casualties as well.