Gunmen in Pakistan said on Monday they had killed 50 hostages after hijacking a train carrying more than 400 passengers, Reuters reported.
The agency notes that it could not independently verify this information.
Dozens of separatist fighters from Balochistan province blew up the train tracks and fired rockets at the train, a security official said.
Pakistani authorities said the attack on the train was over and that all the attackers had been killed, the Associated Press reported.
Security officials said 300 hostages had been rescued and that the operation was ongoing. They did not give details about the hostages killed.
Separatists attacked a train carrying about 450 passengers on Sunday in a tunnel in a remote area of Balochistan province.
The separatist group Balochistan Liberation Army (BLA) claimed responsibility for the attack. A spokesman for the group said it was ready to release the passengers if authorities agreed to release its fighters from prison. The Pakistani government did not comment on the separatist demand.
Authorities said women and children were among those rescued. Security officials said an unknown number of security personnel were also killed.
The rescued passengers have been sent to their hometowns, while the injured are being treated in hospitals in Mach district. Other wounded were taken to the provincial capital, Quetta.
Balochistan province, which borders Iran and Afghanistan, has long been the scene of insurgency, the AP said. Local separatists want greater autonomy from the government in Islamabad and a greater share of the region's natural resources.