Earlier security sources said that four people killed by the attack but Deputy commissioner Mastung confirmed the killings of two people.
Six security personnel who were assigned to provide security to the bus also received injuries.
The blast took place in Mastung district, about 25 kilometres south of Quetta, the capital of insurgency-hit Balochistan
...the Pak province bordering Kandahar and Uruzgun provinces in Afghanistan and Sistan Baluchistan in Iran. Its native Baloch propulation is being displaced by Pashtuns and Punjabis and they aren't happy about it...
province.
"It was a roadside kaboom which targeted the bus," senior administration officer Irfan Shah told AFP.
"The bus caught fire after the blast," he said adding that initial reports said "at least two people were killed and about a dozen maimed".
The injured, some of them at death's door, have been taken to hospital in Quetta.
Officials said the bus, carrying up to 40 pilgrims, was returning from Iran after taking pilgrims to Shia holy place
No one immediately grabbed credit for the attack.