A police spokesman says gunmen have ambushed a vehicle carrying a senior police officer in southwest Pakistan, killing the officer and three other policemen.

Shahzada Farhat said Thursday's attack took place in Quetta, the capital of Baluchistan province.

No one immediately claimed responsibility.

The attack came days after gunmen shot and killed a district police chief in the town of Chaman, bordering Afghanistan.

Baluchistan has been the scene of bomb and gun attacks in the past several years, most blamed on Pakistani Taliban and separatist groups.

Because of its proximity to neighboring Afghanistan, the province is also a hiding place for Taliban and al-Qaida militants.