MOSCOW (Reuters) -Russia on Thursday began a new trial of Robert Gilman, a former U.S. Marine who is already serving a prison sentence for attacking a police officer while drunk, and now faces fresh assault charges, the state-run RIA news agency reported.

In October 2022, Gilman was sentenced to 4-1/2 years - later reduced to 3-1/2 years - in a Russian penal colony for the drunken attack on the police officer which he said he did not remember. He said at the time that he had apologised to Russia and the police officer.

RIA said that a new trial into Gilman had got underway on Thursday in the city of Voronezh 465 km (289 miles) south of Moscow.

It said he faced four charges related to the alleged assault of a prison official and a state investigator on four separate occasions when he had punched the men in the head.

RIA said Gilman, whose lawyers told the TASS news agency at his original trial that he had come to Russia to study and obtain citizenship, had pleaded guilty to all the charges.

RIA said the court, which will reconvene on July 15, will request information about Gilman's health and access to medical treatment. It said Gilman had on Thursday complained several times of food poisoning.

At least a dozen American citizens are being held in Russian prisons or pre-trial detention facilities and the trial of U.S. journalist Evan Gershkovich, who is accused of espionage charges which he denies, began on Wednesday.

(Reporting by ReutersEditing by Andrew Osborn)