KABUL, Afghanistan - Afghan officials say there was an explosion outside the Afghan defense ministry causing multiple casualties, as U.S. defense secretary Chuck Hagel visits the country.

Afghan police spokesman Hashmat Stanekzai says an apparent suicide attacker on a bicycle hit the main entrance to the defense ministry around 9 a.m. local time. Officials are still trying to determine the number of casualties.

Hagel was in a meeting at a coalition facility in Kabul and defense officials say he is in a safe location and unharmed. Reporters traveling with Hagel were in a briefing when they heard the explosion, and were moved to a lower floor of the same building. The official spoke on condition of anonymity because he was not authorized to speak publicly.