Separatist insurgents killed three Pakistan Coast Guard personnel on Sunday in the first-ever attack on one of the maritime authority’s patrol ⁠boats ​operating in the Arabian Sea, security officials said.

Intelligence and police officials said the boat was on a routine patrol in a coastal area close to the Pakistan-Iran border ​when ​the militants opened fire and killed ⁠three on board.

The incident adds to security challenges in Balochistan, a flashpoint of insurgency ‌where armed groups have frequently targeted security forces and infrastructure.

The banned separatist group Balochistan Liberation Army (BLA) claimed responsibility for the attack. “Following the operations on land, the action in maritime boundaries marks a new development in the BLA’s military strategy,” the ⁠BLA said in a ⁠statement.

Authorities have launched an investigation and security has been heightened in ⁠the ‌area, said the intelligence and police sources.

Pakistan ​carried out airstrikes in February that ‌sparked a week-long conflict with Afghanistan. Islamabad blames Kabul for providing safe haven to militant groups ‌including the ​BLA to plan ​and coordinate ​their attacks. The Taliban government has denied the accusation.

Gwadar, an important district with ​a strategic deep-sea port that is a ⁠key node in China’s flagship “Belt and Road” infrastructure initiative, has seen repeated attacks on security forces and installations by ‌Baloch ⁠separatist militants.

Authorities did not respond to requests for comment about the incident.