A concussion bomb was tossed at a Lebanese army checkpoint near the house of Internal Security Forces commander Maj. Gen. Ashraf Rifi in Tripoli , north Lebanon late Sunday. The bomb was tossed from a moving motorcycle, New TV reported. A security source said that the troops arrested the two assailants involved in the 10:30 p.m. attack at the checkpoint. They are Said Rajab and Ahmad Arab. No details on the 2 assailants available as of yet.