A U.S. military aircraft has crashed in the East African nation of Djibouti, killing all four U.S. military personnel on board.

The U.S. Africa Command says the aircraft went down during a routine flight late Saturday about six miles from the Djibouti International Airport.

The statement did not describe the type of aircraft nor the circumstances of the crash.

It says a safety board investigation has been launched to determine the cause of the incident.

Djibouti is host to the only U.S. military base in Africa. The base is home to the U.S. Combined Joint Task Force-Horn of Africa, which has played a role in counter-terrorism and counter-piracy operations.

U.S. Defense Secretary Leon Panetta visited the base in December.