A car bomb attack on a bus in Pakistan's insurgency-hit southwest killed at least three Shiite pilgrims and wounded 25 on Sunday, officials said.
The remotely-triggered bomb hit a convoy of three buses in Mastung district, some 30 kilometres (18 miles) south of Quetta in Baluchistan province.
"One bus was badly damaged. Three Shiite pilgrims were killed and 25 wounded and the death toll may rise," Akbar Hussain Durrani, a senior government official in Quetta, told AFP.
Durrani said some 180 Shiite pilgrims were on their way to Iran when the bomb ripped through one of the buses.
Tufail Baluch, another senior government official, confirmed the blast. "The bomb was planted in a car. The condition of some of the injured is critical," Baluch said.
There was no claim of responsibility for the incident.
Baluchistan, which borders Iran and Afghanistan, has increasingly become a flashpoint for sectarian violence between Pakistan's majority Sunni Muslims and Shiites, who account for around a fifth of the country's 180 million people.
The oil and gas-rich province is also rife with Islamist militancy and a regional insurgency which began in 2004.
The insurgents demand political autonomy and a greater share of profits from the region's natural resources.