An explosion has killed at least six people and injured several others outside a court building in Pakistan’s capital Islamabad, police say, adding some of them are in a critical condition.

“We are probing what kind of blast it was. It is not clear yet. We will be able to provide more details after we get a report from our forensic team,” a police spokesperson said on Tuesday.

The blast occurred near the entrance of Islamabad district court, which is typically crowded with a large number of litigants.

Local media showed gory pictures of the site, with bloodied individuals lying near a police van.