New details have emerged after imprisoned U.S. Marine veteran Paul Whelan was allegedly assaulted by another inmate in a Russian prison.

Whelan, whose family insists he is being held on false charges, suffered an eye injury in a quarrel with another convict, the Mordovian Federal Penitentiary Service told Russian news agency Interfax. 

The agency reported Whelan's assailant is a "convict from Turkey" who allegedly struck the U.S. national "on the basis of political differences." 

"Employees of the institution immediately stopped the illegal actions and took the participants in the conflict to the medical unit," the Federal Penitentiary Service said, according to Interfax. Whelan is reported to have an abrasion under his eye. 

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Paul Whelan

Paul Whelan, a Marine veteran who was arrested for alleged spying, was reportedly assaulted by a fellow inmate at a Russian prison in Mordovia.  (Sofia Sandurskaya, Moscow News Agency photo via AP)

According to the report, the incident was recorded through video surveillance, and an investigation is being conducted for review by police in Mordovia. 

The Whelan family said Paul was assaulted at a labor camp on Tuesday afternoon. David Whelan said his brother was working at a sewing table when a new inmate blocked part of the production line and Paul asked him to move out of the way.

"After repeated requests, the prisoner hit Paul in the face, breaking Paul's glasses in the process, and attempted to hit him a second time," David Whelan said in an email statement. "Paul stood up to block the second hit and other prisoners intervened to prevent the prisoner continuing to attack Paul."

David Whelan said his brother has asked local prosecutors to investigate the alleged attack. 

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Paul Whelan

Paul Whelan listens to the verdict in a courtroom at the Moscow City Court, June 15, 2020. (Sofia Sandurskaya, Moscow News Agency photo via AP)

"He is also concerned that these sorts of attacks can occur any time and, due to the various sharp implements in the workshop including the shears the other prisoner was holding today, could escalate into a far more serious attack," David Whelan said. "Paul is a target because he is an American and anti-American sentiment is not uncommon among the other prisoners."

The U.S. State Department told Fox News Digital the U.S. Embassy in Moscow has been in contact with Paul and understands he is receiving medical treatment. 

The State Department also called on Russia to release Whelan and to ensure all U.S. citizens being detained there are safe. 

Whelan was arrested in December 2018 on charges of espionage and spying for the U.S. government and sentenced to 16 years. He and the U.S. have denied the charges as the 53-year-old remains imprisoned at a labor camp in Russia's Mordovia republic.

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On Dec. 28, 2018, while staying in a hotel in the Moscow area, Whelan was arrested by the Russian Federal Security Service. At the time, he had reportedly arrived in the Russian capital to attend the wedding of a friend and act as a travel guide for the groom's family. However, Russian officials claimed that Whelan had met with an unnamed Russian citizen who gave the former Marine a USB drive containing classified material.

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He was left out of the highly publicized prisoner exchange between the U.S. and Russia last year in which WNBA player Brittney Griner was freed from Russian custody for the release of Russian arms dealer Viktor Bout, nicknamed the "Merchant of Death."

Fox News Digital's Louis Casiano contributed to this report.