QUETTA, Pakistan - At least three militants were killed by Pakistani security forces and six were injured in a grenade attack in two attacks on Friday following a search for insurgents who had attacked two military bases, killing seven soldiers and 13 of their own, in the latest violence in southwest Pakistan.

At least three militants, including two 'high value targets' were killed in a clearance operation conducted in Kech district to flush out militants from hideouts linked to Wednesday’s attacks on military bases in Balochitan province,” Pakistan’s military media wing said on Friday night.

In another attack, at Chaman, a town bordering Afghanistan at least six people were injured in a grenade attack at para-military post.

The Wednesday attacks, the biggest in recent years by ethnic Baloch insurgents, came hours before Pakistani Prime Minister Imran Khan arrived in Beijing for the opening of the Winter Olympics, where he will have meetings with Chinese President Xi Jinping and other leaders. 

Two Pakistani security officials, requesting anonymity as they are not permitted to speak publicly, said the operation was not yet over.

"The army is conducting search operations in the area. There might be some more elements hiding in the surroundings," one official told Reuters.

The army said the attacks were simultaneous and coordinated.

"They used explosive-laden vehicles at gates, they have the latest weaponry left behind by NATO forces," Sheikh Rasheed Ahmad, Minister of Interior said on Friday, adding that the attack was defeated and both bases were under the control of the Pakistani military.

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

The Baloch Liberation Army (BLA) group said it was behind the attacks in a statement sent to a Reuters reporter, adding that one of the two bases was still under its control after 38 hours. This could not immediately be verified independently.

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.

Islamabad blames arch-rival India for supporting the insurgency, a charge Delhi denies, and says such anti-Pakistan groups often use neighbouring Afghanistan to plan attacks - a charge denied by Taliban government spokesman Bilal Karimi.

India's external affairs ministry did not respond to a request for comment.

(Additional reporting by Asif Shahzad in Islamabad, Raza Hassan in Karachi Editing by Louise Heavens) ((raza.hassan@thomsonreuters.com;))