At least six police personnel were killed and 15 security officials injured after three suicide bombers attacked Pakistan’s Quetta on Tuesday, Reuters reported.

“It is a suicide attack, and we have a confirmation that six of our police officials are dead,” provincial police chief Moazzam Jah Ansari told the news agency. Two suicide bombers attempted to strike a paramilitary checkpoint on the city’s border and another targeted a police truck.

No group has claimed responsibility for the attack yet.

The city has been a target in several attacks. On April 3, unidentified bike-borne men shot dead four members of a Christian family in the city. In December 2017, at least 10 people were killed and 44 were injured in a suicide attack at a Christian church in Balochistan’s Quetta.