BEIRUT, June 20 (Reuters) - A suicide bomber at a checkpoint in Leba**n appeared to have been targeting a convoy of the country's top security chief when he blew himself on Friday, a security source said. The security official, Abbas Ibrahim, passed through the checkpoint in Leba**n's Bekaa valley minutes before the bomber detonated the explosives which killed one and wounded 37. (Reporting by Lalia Bassam, Writing by Sylvia Westall, Editing by Samia Nakhoul)