A loud explosion was heard in Afghan capital, Kabul, on Thursday, witnesses and officials said.
The blast shook windows and doors in an area close to foreign embassies and government buildings.
The blast took place in Shash Darak, a heavily fortified area adjacent to the Green Zone and home to several important complexes including the National Directorate of Security (NDS), the Afghan intelligence service.
An Afghan security official told AFP there had been casualties, and that the blast took place near a checkpoint.
Interior Ministry spokesman Nasrat Rahimi said a car bomb had exploded on a main road and police were sealing off the area.
The Taliban claimed responsibility for the attack.
Zabihullah Mujahid, a Taliban spokesman, said three vehicles were destroyed, 12 foreigners and eight members of the Afghan forces were killed, but the Afghan government rejected the casualty figures claimed by the Taliban.