A police official said a suicide bomber had struck in the Afghan capital, Kabul, after a loud explosion was heard in an area close to foreign embassies on Friday.
Police sirens could be heard in the area but there was no immediate word on any casualties from the blast.
Bismillah Tabaan, the police commander of the city's ninth district where the explosion took place, said the cause of the blast was a suicide bombing but details, including the target, were not yet clear.
Interior ministry spokesman Najib Danish said the cause of the explosion was a car bomb in the Qabl Bai area of the city. At least four civilians had been wounded, he said.
The attack came two days after President Ashraf Ghani offered to start peace talks with the Taliban and just over a month after an explosives-packed ambulance was detonated in the city centre, killing around 100 people.
There was no immediate claim of responsibility for the latest blast.
Much of the centre of Kabul is already a zone of concrete blast walls, razor wire and police checkpoints but security has been tightened even further in the wake of the Jan. 27 ambulance attack and another attack on the city's Intercontinental Hotel earlier in the month.