KABUL: A huge explosion shook Kabul early Friday, witnesses in the Afghan capital said, but there was no immediate confirmation of the cause.

The explosion was followed by sirens, and a loudspeaker announcement telling residents of the city to stay inside.

Scattered gunfire could also be heard.

Kabul has been relatively peaceful for a month, with the last major incident on January 18 when gunmen stormed the commercial heart of the city, taking over buildings, detonating suicide vests and killing at least five people.