Pakistan's army says 21 hostages have been killed after armed separatist militants seized a train in Pakistan.
The military's spokesperson Ahmed Sharif Chaudhry also confirmed 33 militants from the Baloch Liberation Army had also been killed.
Security officials said that some 300 hostages were rescued in the day-long operation, in the Balochistan province.
Pakistani authorities became involved in a stand-off with insurgents on Tuesday, after the train carrying hundreds of passengers was captured.
In an earlier statement on Wednesday, the BLA claimed to have killed 50 captives, after previously threatening to do so if Pakistani authorities intervened.
The BLA said it would release the passengers if authorities freed jailed militants, but the Pakistan government did not comment and had rejected similar calls in the past.
Security forces were being cautious on Wednesday, with officials saying the hostages were surrounded by BLA militants wearing vests loaded with explosives.
"They are wearing suicide vests and … that's making the rescue difficult," Pakistan's junior interior minister Talal Chaudhry told Geo television.
"The operation is being conducted very carefully so that no harm is inflicted to the hostages, the women and children."
Government spokesperson Shahid Rind said the Pakistani forces were being backed up by helicopters in the remote region.
He described the attack as "an act of terrorism".
An AFP photographer in Quetta, the provincial capital, witnessed about 140 empty coffins being transported by train to the incident site on Wednesday, local time.
More than 400 people were on the Jaffar Express train when it was hijacked on Tuesday as it entered a tunnel in Bolan, a district in restive Balochistan province.
The group shared a message from one of its fighters on the train, calling on people in Balochistan to join their fight against the Pakistani state.
"Comrades are shedding their blood for you, for this motherland," the man said in the message, posted on Telegram.
The BLA regularly targets Pakistani security forces but has also in the past attacked civilians, including Chinese nationals working on multi-billion-dollar projects related to the China-Pakistan Economic Corridor (CPEC).
Pakistan hosts thousands of Chinese workers as part of Beijing's multi-billion-dollar Belt and Road Initiative, which is building major infrastructure projects including ports and airports in Balochistan.
Authorities said the hostages rescued included women and children.
According to the officials, the train was partially inside a tunnel when about 50 militants blew up the tracks and immobilised the engine and its nine coaches.
[Pakistan map]The driver was critically wounded by gunfire and guards aboard the train were attacked, although the officials gave no details on the number of guards who were aboard or their fate.
A security source told Reuters that after taking control of the train, the insurgents began pulling passengers off and checking their identification.
"They were looking for soldiers and security personnel," the official said.
Rescued passengers were sent on Wednesday to their home towns and the injured were being treated at hospitals in the Mach district in Balochistan. Others were taken to Quetta about 100 kilometres away.
The train was travelling from the provincial capital, Quetta, to the northern city of Peshawar when the attack took place.
A woman, who said her son was among the passengers still held hostage, confronted provincial minister Mir Zahoor Buledi when he visited the freed passengers.
"I beg you with folded hands, please bring my child back. Why didn't you stop the trains if they were not safe? If the train was never going to reach its destination, why let it depart?" she said.
Pakistan Railways suspended all operations from Punjab and Sindh provinces to Balochistan until security agencies confirm the area is safe, according to local media reports on Wednesday.
Mr Buledi told reporters that the government was working to improve the security situation in the region.
Balochistan, which borders Iran and Afghanistan, has long been a hotspot for separatist insurgencies in those countries, with militants demanding greater autonomy and a larger share of the region's natural resources. The main insurgencies, however, have centred on Pakistan and Iran.
Insurgencies on either side of the Iran-Pakistan border have frustrated both countries. Their governments suspect each other of supporting — or at least tolerating — some of the groups operating on the other side of the border.
In Iran, the militant group Jaish al-Adl has carried out many attacks in recent years. Tehran has sought help from Pakistan in countering the threat from Jaish al-Adl, and Pakistan also wants Tehran to deny sanctuary to BLA fighters.
In January last year, the two nations engaged in a tit-for-tat air strike targeting insurgents inside each other's border areas, killing at least 11 people, but later they quickly de-escalated the situation through talks.
The BLA, which has waged a years-long insurgency in Pakistan, said the hostages and some captured members of the security forces were being guarded by suicide bombers.
The BLA has warned that the hostages' lives will be at risk if the government does not negotiate.
Trains in Balochistan typically have security personnel on board as members of the military frequently use them to travel from Quetta to other parts of the country.
Militants have attacked trains in the past but have never managed to hijack one. In November, a separatist group carried out a suicide bombing at a train station in Quetta that killed 26 people.
[THE WORLD YOUTUBE PKG]Pakistani authorities and analysts estimate that the BLA has about 3,000 fighters. Some analysts say the train attack and its focus on civilians could backfire.
"After failing to damage the Pakistan Army within Balochistan, BLA has shifted its targets from military to unarmed civilians," Syed Muhammad Ali, an Islamabad-based independent security analyst said.
"This may give them instant public and media attention, but it will weaken their support base within the civilian population, which is their ultimate objective."
ABC/wires
