France called on Friday for the immediate release of French researcher Laurent Vinatier by Russia as it welcomed Thursday's major prisoner exchange that resulted in the release 16 prisoners from Russia to the West, Paralel.Az reports citing Reuters.

Vinatier in June pleaded guilty to a charge of failing to register as a foreign agent while gathering information on the Russian military, and faces up to five years in prison.

A Russian court this week extended the pre-trial detention of Vinatier until Sept 5.

"Our thoughts are with those people who remain held in custody arbitrarily in Russia, most notably such as our compatriot Laurent Vinatier," the French foreign ministry said in a statement. "France calls for their immediate release."

On Thursday, U.S. journalist Evan Gershkovich and ex-U.S. Marine Paul Whelan were among three U.S. citizens returned to the United States, hours after being freed from Russian detention as part of the biggest prisoner exchange between the two countries since the Cold War.