Russia has sentenced an elderly decorated space engineer and university instructor to seven years in prison for state treason, an official said Friday.

Vladimir Lapygin was sentenced to seven years on charges of state treason, a spokesman for Moscow City Court told AFP, without giving details.

"The verdict was pronounced on September 6," he said, adding that the entire case was "top secret."

Russian agencies said Lapygin taught at Moscow's Bauman State Technical Institute. Information on the university's page suggested he advised graduate students in the mechanical engineering department.

Lapygin is also an employee of Tsniimash, the Central Research Institute of Machine Building, which develops rockets and is administered by the Roscosmos space agency.

In 2014 he received a medal for his contributions to Russia's economy and defence capabilities.

Russian media said Lapygin is in his late 70s and spent months under house arrest after his initial detention in May 2015. Lapygin was reportedly accused of giving Russian secrets to China.

Lapygin is just the latest person convicted for state treason and espionage in a list of Russians and foreigners which has been growing rapidly since 2014 and has included an air traffic controller, a housewife and a former intelligence officer.