A bomb explosion at an office of the International Committee of the Red Cross in northwestern Pakistan on Saturday damaged four vehicles, but injured no one, police said.
It was not immediately clear who was behind the early morning attack at the aid agency's office in Peshawar, the capital of North West Frontier Province, bordering Afghanistan, the AP reports.
The city's police chief, Iftikhar Khan, said the incident was being investigated.
"Someone threw the explosive device at the ICRC office, but it didn't cause any casualties as the office was closed at the time," he said.
Khan provided no further details.
ICRC public relations officials could not immediately be reached for comment.
Pakistan is a key ally of the United States in its campaign against terrorism. Offices of international aid agencies and Westerners have been attacked in the Islamic nation since the attacks in the U.S. on Sept. 11, 2001.