Kamal Chauhan, a disgruntled RSS worker arrested by the NIA, on Wednesday claimed that he had planted bombs on board Samjhauta Express in 2007 that left 68 people, mostly Pakistanis, dead.

"Yes, I have done it on my will," Chauhan told mediapersons as he was being taken out after in-camera proceedings in Panchkula court which today granted NIA his custody till February 24 for questioning him on his alleged role in the blast in the Delhi-Lahore train.

His remarks came as NIA alleged that Indore-based Chauhan had planted bombs on board Samjhauta Express and had undergone training in arms and explosives in Haryana and Madhya Pradesh.

"Investigations reveal that Chauhan along with Ramchandra Kalasangra alias Ramji and Lokesh Sharma, also charged in the case, planted the explosives in the train at Old Delhi, from where the train originates," NIA's Special Prosecutor R K Handa said outside the court.

Chauhan, believed to be a close aide of Kalsangra and Sandeep Dange, key accused in the Samjhauta case, was arrested in Noida on Delhi's outskirts on Sunday and was brought to Panchkula in Haryana today. The NIA had sought his remand for a fortnight.

"We have to unearth his complete involvement and association. During investigations, it has come to light that Chauhan underwent extensive training in handling of weapons and explosives. He took training at Karni Singh shooting range in Faridabad (Haryana) and a register seized by CBI on August 10, 2011 has the entries of his name in that shooting range.

He also took explosives and arms training at Bagli in Dewas (Madhya Pradesh)," Handa said

Chauhan, born in Mhow, was an activist of Rashtirya Swayamsevak Sangh. Sources claimed that during interrogation, Chauhan had spoken about his association with the RSS and his fall out as he did not subscribe to the "new ideologies".

Meanwhile, Chauhan's counsel Anil Soni and Shailender Babbar alleged that his arrest was "politically motivated" and aimed at influencing polls in Uttar Pradesh while his family claimed that he is a farmer by profession and in "no way involved in the crime".