A Russian court has sentenced former United States marine Paul Whelan to 16 years in a maximum security prison colony on espionage charges.

The Moscow City Court’s verdict on Friday was condemned by the US envoy to Russia who said it was based on a “secret trial in which no evidence was produced”.

Whelan stood in the courtroom defendant’s cage with a sign that read “Sham trial!” and called on the US president to intervene.

He was accused of having obtained classified Russian state information, the nature of which has not been disclosed.

US Ambassador John Sullivan, who was present at the court in Moscow, slammed the proceedings as an “egregious violation of human rights and international legal norms”, a statement by the US embassy said.

Whelan, 50, has been in Russian custody for the past year and a half.

A flash drive and documents were confiscated from Whelan while he was arrested on a trip to Moscow in December 2018. No further details about the evidence have been revealed.

Whelan has insisted that he is innocent. His family has said he was visiting Russia to attend a wedding.