Three youths killed a 45-year-old woman on a running train before her family when she objected to their smoking, one of them strangling her with his foot after she collapsed from their blows, her son said.

Ranjeet Kumar, 24, said none of the other passengers in the crowded general compartment came to the aid of his mother Chinta Devi, who was attacked early on Saturday while the Jallianwalabagh Express passed through Shahjahanpur district, 175km northwest of Lucknow.

Government Railway Police have arrested a young man, Sonu Kumar, and are looking for two other suspects, the GRP station house officer in Shahjahanpur, Arvind Pandey, said.

Ranjeet told reporters he had boarded the Tatanagar-bound train with his mother and pregnant wife Babita Devi in Amritsar, where he works, and were travelling to Dehri-on-Sone in Bihar, from where they planned to bus to hometown Dalmianagar in Rohtas district for Chhath.

The three youths, who he said seemed to be between 25 and 30, were smoking continuously in the compartment.

“My mother was feeling suffocated and was also concerned about the health of my pregnant wife. So, as the train left Bareilly station at 2am, she asked the youths to stand near the door and smoke. They refused,” Ranjeet said.

“A while later, she again asked them to stop smoking inside the compartment and they again ignored her. When my mother shouted at them, they began hitting her. They beat me and my wife when we tried to save her.

“My mother collapsed to the floor. One of them then started strangling her with his foot while the other two kept kicking her. She became motionless after two-three minutes.”

“We have arrested one of the accused and are searching for the other two, who had jumped off the train and run away before it reached Shahjahanpur junction at 3.30am,” Pandey, the station house officer, said.

Sonu belongs to Azamgarh district in Uttar Pradesh, officers said, adding that he had revealed that the two other suspects were from the same place and that all three worked at a cement factory in Amritsar.

Chief minister Yogi Adityanath had held a videoconference with senior administrative and police officers last week, asking them to ensure that people returning home on trains and buses for Diwali and Chhath did not face any inconvenience.