A Russian court on Monday sentenced a 72-year-old American in a closed trial to nearly seven years in prison for allegedly fighting as a mercenary in Ukraine.

Prosecutors said Stephen Hubbard signed a contract with the Ukrainian military after Russia sent troops into Ukraine in February 2022, and he fought alongside them until being captured two months later.

He was sentenced to six years and 10 months in a general-security prison. Prosecutors had called for a sentence of seven years in a maximum-security prison.

Hubbard, from the state of Michigan, is the first American known to have been convicted on charges of fighting as a mercenary in the Ukrainian conflict.

The charges carried a potential sentence of 15 years, but prosecutors asked that his age be taken into account along with his admission of guilt, Russian news reports said.

Arrests of Americans have become increasingly common in Russia in recent years. Concern has risen that Russia could be targeting US nationals for arrest to use later as bargaining chips in talks to bring back Russians convicted of crimes in the US and Europe.