A suicide bomber on foot detonated explosives outside the main foreign military base in Afghanistan's southern Kandahar on Tuesday, killing himself, but there were no reports of any other casualties, officials said.
A spokeswoman for NATO-led forces in Kabul, Lieutenant Commander Katie Kendrick, said there was small-arms fire outside the base and that the bomber had tried to gain access through one of the gates.
"The suicide bomber failed to gain access and then detonated his explosives, killing himself. This appears to be an unsuccesful and unorganised attack," said Kendrick.
Kendrick did not have any more details on the attack or how many people were involved and said there were no reports so far of any other casualties.
A Reuters witness inside the base said he heard what sounded like two rockets followed by gunfire.
Kandahar Air Field, 25 km (15 miles) outside Kandahar city in southern Afghanistan, is the largest foreign military base in the country and home to tens of thousands of troops and civilian workers.
The airfield often comes under insurgent rocket attack but it is rare for militants to launch a ground assault on the sprawling and heavily fortified base. One in May, however, left a number of troops and civilian staff wounded.
Kandahar, the spiritual home of the Taliban, is the main focus of Washington's strategy to try to turn the tide against the insurgency this year.
Thousands of U.S. troops are engaged in operations in outlying districts while others have moved inside the city with Afghan police in a bid to bring better security.