Media playback is unsupported on your device Media caption The BBC's Aleem Maqbool: "Mastung... is a place where there've been many attacks in the past"

At least 19 Shia Muslim pilgrims have been killed by a bomb attack on a bus convoy in southwest Pakistan, local officials say.

More than 20 people have been injured in the incident in the Mastung district of Baluchistan province.

Pakistan has experienced worsening sectarian violence in recent years. Last month 23 Shia Muslims were killed by a bomb in the city of Rawalpindi.

No group has yet said it carried out Sunday's bombing.

Initial reports said it had been detonated by remote control but a government official said it had been a suicide attack.

Officials said that some of those injured were in a critical condition and that the death toll may rise.

The bus convoy had reportedly been on their way to neighbouring Iran, a Shia-majority country and popular pilgrimage destination.