Lebanon's army launched heavy artillery barrages into a besieged Palestinian refugee camp in north Lebanon on Tuesday in its continued struggle to overtake Islamic militants holed up inside. The renewed fighting comes a day after a mortar shell fired by Fatah Islam militants inside the Nahr el-Bared camp killed two Lebanese Red Cross workers and injured a third. A senior military official said Tuesday that the army was reinforcing its positions and "tightening the noose" on the militants inside the camp. The official again urged Fatah Islam fighters to turn themselves in. The fighting in the Nahr el-Bared camp which began on May 20 has dragged on for more than three weeks with no imminent end in sight.