The explosion killed at least 24 people and injured around 70, according to three provincial government and security officials, who spoke on the condition of anonymity as they are not authorised to speak to the media.
Sunday's attack was the latest in a series of strikes on trains, security forces and infrastructure in the mineral-rich province that borders Iran and Afghanistan, where Pakistan has launched counterinsurgency operations after some of the deadliest violence in years.
The separatist militant group Baloch Liberation Army, or BLA, said in a statement to media that it carried out the attack and described it as a suicide bombing. Reuters could not independently verify the claim.
The shuttle train was carrying passengers from Quetta's cantonment area to connect with the Jaffar Express long-distance train when the blast struck near a railway track in the provincial capital, Pakistan's railways ministry said in a statement.
The explosion derailed the engine and three coaches, while two coaches overturned, the ministry said, adding that security forces had cordoned off the area and rescue operations were under way.
A security official said an explosives-laden vehicle hit one of the train's bogies in a residential area, and that some of those killed were residents of a nearby apartment building.
Images from the scene showed burnt-out vehicles, damaged residential buildings, twisted metal and debris scattered near the railway track, with smoke rising from the wreckage.
Prime Minister Shehbaz Sharif condemned what he called a "heinous bomb explosion" in a post on social media website X.
He expressed condolences for the victims' families and said the nation stood with the people of Balochistan.
In March 2025, BLA militants hijacked the Jaffar Express train, taking hundreds hostage before a military operation ended the day-long stand-off. The military said 21 hostages, four troops and all 33 attackers were killed.
Earlier this year, Pakistani forces killed 145 militants in a 40-hour operation after co-ordinated attacks across Balochistan left nearly 50 people dead, provincial officials said.
