Balochistan was rocked by a series of attacks late last year that claimed over 180 lives and raised concerns about a growing militant presence.
The train was travelling from Baluchistan’s capital of Quetta to the eastern metropolis of Lahore when a blast on the main railway track damaged one of its cars.
ISIS claimed responsibility for the attack via its Amaq news service.
Gunmen on Thursday shot and killed a Pakistani regional opposition leader in the latest violence in the southwestern province of Baluchistan.
Pakistan is one of just three countries in the world, along with Afghanistan and Nigeria, that have endemic polio.