A passenger on the Moscow metro was seriously injured after being stabbed in the chest during an ethnically charged brawl that broke out on a moving train, Interfax reported.

The injured passenger, an unemployed Moscow resident, was hospitalized in grave condition following the bloody altercation involving nine people — four of them immigrants from Kyrgyzstan — on the Arbatsko-Pokrovskaya line.

The fight began late Monday after the train left Baumanskaya station, then spilled onto the platform when it pulled into the next stop at Electrozavodskaya station.

"After the train stopped, the fight continued on the platform. A police officer on the platform arrested six of the brawlers, who were in a state of inebriation. Among them were two citizens of Kyrgyzstan," an unnamed police source told the news agency.

The officer was also injured while breaking up the fight, but other cops later detained two others — also Kyrgyz citizens — in the Bishkek Night cafe in northwestern Moscow.

Both had not registered since arriving in Russia on July 1, 2011, and are being kept in pretrial detention, Interfax reported.

The six people originally detained were given administrative sentences and — after sobering up — were sent to investigators for further questioning.