Separatist insurgents have claimed responsibility for an attack on a Pakistani army post near a southwestern port in which China is investing, and the army said 10 soldiers were killed.

The attack, launched late on Tuesday in Kech district, north of Gwadar port, was the heaviest in years in a low-key insurgency that ethnic Baloch insurgents have been waging against the Pakistani government.

“We are resolute in our commitment to rid Pakistan of all forms of terrorism,” Prime Minister Imran Khan said in a statement on Friday in which he paid tribute to the 10 “martyred” soldiers.

The army said it killed one of the attackers and arrested three in a clearance operation that was still going on.

The Baloch Liberation Front (BLF) insurgent group claimed responsibility for the attack, saying in a statement sent to a Reuters reporter that 17 soldiers and one of its members were killed.

Ethnic Baloch guerrillas have been fighting the government for decades for a separate state, saying Pakistan’s central government unfairly exploit the rich gas and mineral resources of Balochistan province, which shares borders with Afghanistan and Iran.

China is involved in the development of the Gwadar port on the Arabian Sea and other projects in the province as part of a

$60 billion China-Pakistan Economic Corridor, which is itself

part of Beijing’s Belt and Road initiative.

The insurgents often target gas projects as well as infrastructure and security posts in the province but have begun launching attacks in other parts of Pakistan.

They also attack Chinese projects, and occasionally kill Chinese workers despite Pakistani assurances that it is doing everything it can to protect the Chinese projects.

Pakistan has also accused India of covertly supporting the insurgents. India denies that.