Pakistani police say a gunman riding on a motorcycle shot to death a senior police officer who has been investigating sectarian killings allegedly carried out by a Sunni Muslim militant group.

Police officer Zubair Mahmood said the gunman ambushed Jamil Kakar's car as he was on his way to a Supreme Court hearing Friday in Quetta, the capital of southwestern Baluchistan province.

No group has claimed responsibility for the attack, but suspicion is likely to fall on Lashkar-e-Jhangvi, a Sunni militant group blamed for a rise in attacks against Shiite Muslims in Baluchistan in recent months.

Kakar was one of the highest ranking police officers in Quetta and played a key role in investigating Lashkar-e-Jhangvi.