Pakistan's army successfully repulsed an insurgent night attack on two southwestern bases that killed four soldiers and 15 rebels, Interior Minister Sheikh Rasheed Ahmad said on Thursday.

A clearance operation is underway in the province of Balochistan, the minister added in a recorded video statement.

The overnight attacks came hours before Prime Minister Imran Khan set off for Beijing for the opening of the Winter Olympic Games.

"We salute our brave security forces who repulsed terrorist attacks," Khan said in a statement on Thursday.

The Baloch Liberation Army (BLF) insurgent group claimed responsibility in a statement sent to a Reuters reporter, saying its suicide bombers had detonated explosive-laden vehicles at the entrance of the bases killing more than 50 soldiers.

Last week, the insurgents killed 10 soldiers in an attack on a post near the port of Gwadar on the Arabian Sea, the heaviest casualty toll for the army in the Balochistan insurgency in years.

The army said both of the Wednesday night attacks – one in Panjgur district and the other in Naushki district – had been repulsed.

Ethnic Baloch guerrillas have been fighting the government for decades for a separate state, saying the central government unfairly exploits Balochistan's rich gas and mineral resources.

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

China is involved in the development of the Gwadar port and other projects in the province as part of a $60 billion China-Pakistan Economic Corridor, which is part of Beijing's Belt and Road initiative.

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