BEIRUT, Lebanon (AP) _ A hand grenade slipped from the belt of a Lebanese army officer and exploded today at a hospital in east Beirut. Police said the officer was killed and four visitors were injured.

The grenade exploded in the morning in the visitors' lounge of the Hayek Hospital in the Christian district of Sin el-Fil, a police spokesman said.

First Lt. Issam Rahmeh, who was visiting a patient, died instantly and four other visitors were injured, said the spokesman, who cannot be named in line with standing regulations.

He said it had not been determined how the grenade slipped from Rahmeh's belt. The army was investigating the incident.