At least 140 people were killed when a lorry transporting oil burst into flames near the Pakistani city of Ahmedpur East, local officials say, according to BBC.
A crowd had gathered reportedly to collect fuel leaking from the overturned vehicle when it caught fire.
Dozens are being treated in hospital.
It appears the tanker blew a tyre while rounding a sharp bend in the road.
The subsequent fire may have been sparked by someone lighting a cigarette, rescue services say.
The country's roads are notoriously dangerous, with poor vehicle maintenance and reckless driving contributing to the problem.
Army helicopters were dispatched to ferry casualties to hospitals, army spokesman Major Gen Asif Ghafoor said in a tweet.