At least nine police officers were killed and 16 others were injured today in suicide attack against the bus they were riding in southwest Pakistan, police said.

“The suicide bomber was riding a motorcycle and crashed into the back of the bus,” said Abdul Hai Amir, a local police official.

The attack took place in the city Dadar in the Katchi district, about 120 kilometers southeast of Quetta, the capital of Balochistan province.

The death toll may rise as eight injured are in critical condition.

It is the latest in a series of attacks on police officers in Pakistan. Currently no organization has not taken responsibility.

Balochistan is a large, poor and sparsely populated province of Pakistan, bordering Afghanistan and Iran. The province is rich in hydrocarbons and minerals, but its residents — nearly 12 million people — complain that the Pakistani government has marginalized them and is stealing the region’s natural resources.

For years it has been the scene of violent conflicts between different ethnic and religious groups. In the region, police are often the target of attacks by local insurgent groups or the Pakistani Taliban.