PESHAWAR, Pakistan (AP) — The death toll from a suicide attack on a security post in northwest Pakistan rose to 14 police officers early Sunday, authorities said as a self-proclaimed breakaway group of the Pakistani Taliban claimed responsibility for the attack.

A suicide bomber and several gunmen detonated an explosives-laden vehicle near the post in Bannu, a district in Khyber Pakhtunkhwa province bordering Afghanistan, late on Saturday, senior police official Sajjad Khan said. The attack triggered a shootout, and some officers were killed in the exchange, while others died later after the building collapsed.

Rescuers searched for hours and used heavy machinery to retrieve bodies from under the rubble, Khan said, adding that three police officers were wounded in the attack.

Meanwhile, hundreds gathered at the Bannu police headquarters for the funerals of the slain officers. Uniformed colleagues stood in silence as coffins, draped in the national flag, were carried past grieving families. Some relatives broke down upon seeing the coffins. A Muslim cleric led funeral prayers under tight security. Security forces have launched an operation to track down the perpetrators.

A newly formed militant group, Ittehad-ul-Mujahideen Pakistan, claimed responsibility for the attack in a statement sent to reporters.