The group issued the denial in a video statement on Sunday via its accounts on Telegram and RocketChat.

The speaker in the video delivered the message in Arabic and Hausa.

The video showed at least seven masked militants carrying guns.

The unidentified speaker, who stood in the middle, referred to the "false claim circulating among people that Ansarul al-Muslimin fi Bilad al-Sudan [full name of the group] had claimed responsibility for the train attack".

He said "this is an utter lie and fabrication that has no basis of truth," and said that Ansaru had nothing to do with the train attack or the abduction of passengers.

It is unclear what "false" Ansaru claim of responsibility the speaker was referring to.

Nigerian officials blamed Ansaru and Boko Haram, which is active in the north-east, for the attack in the north-western state of Kaduna.

The gunmen who carried out the attack have released videos of hostages pleading with the authorities to help secure their release.

Ansaru said it believed the attack "has nothing to do with jihad" and that such acts "cause fitna [dissonance and conflict] and aversion".