Police and rescue officials say a suicide bomber who had hidden explosives in a car killed at least 12 people and injured dozens on Saturday when it exploded near a roadside police checkpoint in Dera Ismail Khan district of Pakistan’s Khyber Pakhtunkhwa province.

Two officers from the customs and excise were among those killed in the blast, police said. Other casualties were reportedly also security staff and passersby. Several of the injured were said to be in critical condition after the attack.

A team from the Darazinda station arrived on the scene and started its rescue operation. The injured and the dead were taken to a nearby hospital for medical and treatment. Teams of bomb disposal experts were also deployed to the area to look for explosives and ascertain the type of explosive material used.

But more violence erupted later, as gunmen reportedly opened fire on an ambulance that arrived at the scene to help victims. Province Emergency service informant Bilal Faizi said the shooting was confirmed, whereas local Police chief Safdar Baloch stated that numerous security personnel and civilians transiting through the region fell victim of the shooting.

Pakistani Islamists group the Tehrik-e-Taliban Pakistan (TTP) attributed the attack to its. The group is not affiliated with the Taliban of Afghanistan, but has not been unlinked from the Afghan Taliban in the past.

The bombing comes just following a series of security incidents reported in Khyber Pakhtunkhwa. A week ago, another attack took place in which a vehicle with explosives was driven into a mosque in Kohat district. It is reported to have damaged the mosque, and caused part of the outer wall of adjacent police offices to collapse.

Police are still working on the Dera Ismail Khan attack, but are still trying to reckon the full number of deaths and injuries.