Pakistan on Monday summoned a senior Afghan diplomat and lodged a formal protest over a suicide attack in the northwestern district of Bannu that killed 15 police officers.

The attack took place late Saturday in Bannu, near the border with Afghanistan.

Pakistani authorities blamed the attack on Tehrik-e-Taliban Pakistan, also known as the Pakistani Taliban or TTP.

In a statement, Ministry of Foreign Affairs of Pakistan said the protest was conveyed to Afghanistan’s charge d'affaires in Islamabad. It said a detailed investigation, along with evidence and technical intelligence, suggested that the attack was planned by militants based in Afghanistan.

Pakistan also told Kabul that it reserved the right to take decisive action against those responsible for the attack.

There was no immediate response from the Afghan authorities.

According to police, a suicide bomber drove an explosives-laden vehicle into a security post in Bannu. Several gunmen then launched an assault, triggering a gunfight.

Some officers were killed in the exchange of fire, while others died when part of the building collapsed. Four officers were also injured.

A newly formed militant group, Ittehad-ul-Mujahideen Pakistan, claimed responsibility for the attack. Pakistani officials say the group is a front for the TTP.

Pakistan has repeatedly accused the Taliban administration in Afghanistan of allowing TTP militants to use Afghan territory to launch attacks inside Pakistan. Kabul has denied the allegations.

Militant violence has increased in Pakistan in recent years, with many of the attacks linked to the TTP.

Relations between Islamabad and Kabul have remained tense, with border clashes since late February leaving hundreds dead. Although peace talks were held in April with mediation by China, occasional cross-border skirmishes have continued.