Dmitry Kolker had been taken to Moscow's Lefortovo prison, lawyer Alexander Fedulov says

A top Russian scientist has died of cancer two days after he was arrested on charges of state treason and accused of spying for China, his lawyer and family said on Sunday.

Dmitry Kolker, was allegedly dragged from his hospital bed in Novosibirsk, Siberia, and flown to Moscow’s Lefortovo prison.

He passed away within two days, and his family believe his death was partly down to his mistreatment at the hands of Federal Security Service (FSB) officers.

‘He died yesterday. Tomorrow we will lodge a complaint over his detention,’ lawyer Alexander Fedulov said.

Kolker, a doctor of physics and maths, was the head of the quantum optical technologies lab at the Novosibirsk State University.

He was regarded as a world expert on lasers, leading to the accusation that he had colluded with the Chinese security service  a charge he and his family denied.

The scientist had travelled to China on a lecturing trip, his son said, but had been accompanied by an FSB agent at all times

Kolker, who had stage four cancer, was too weak for chemotherapy when he was detained.

The FSB claims it had medical authorisation to unplug him from his hospital bed and transport him to prison.

A number of Russian scientists have been accused of passing on state secrets and charged with treason in recent years.

The charge is punishable by up to 20 years in prison.

Following Kolker’s arrest, a second scientist was detained in the same Siberian city but it wasn’t immediately clear if the two cases were linked.

Antoly Maslov, a chief scientist at an institute of theoretical and applied mechanics, was also transferred to Lefortovo prison.

He was accused of sharing hypersonic state secrets to a foreign power, believed to be China.