LONDON — A bomb ripped through a stationary train in western Pakistan on Tuesday, killing 14 passengers and wounding at least 40, half of them seriously, in a new escalation of the long-running conflict in Baluchistan Province.

Four children and three women were among those killed in the attack, for which a little-known separatist group that was variously named as the United Baluch Army and the United Baluch Liberation Army claimed responsibility.

The bomb exploded in a train car reserved for men soon after the train pulled into Sibi, a small town east of the provincial capital, Quetta. Television footage showed the train on fire, flames licking through its windows, inside a smoke-filled railway station strewn with debris.

A spokesman for the Baluch group told reporters that the attack was in retaliation for a military operation on Monday. The paramilitary Frontier Corps said it had killed 30 separatists during an operation in Khuzdar District. There was no independent confirmation of the toll.