At least 30 dead had been transported to surrounding hospitals, senior district police official Umar Tufail told local television channel Geo News, Reuters reported.
He said he expected the toll to shoot up as there were still mangled train compartments that rescuers had not been able to access despite the passage of hours since the accident in the Ghotki district of the southern Sindh province.
He said there were up to 25 people in one compartment yet to be accessed.
The Sir Syed Express train collided with the Millat Express train in Sindh province between railway stations, according to railway officials.
Rescue operations are continuing at the site of the incident.
MAH/PR