Russian security forces have shot dead two people suspected of "terrorism" in the city of Nizhny Novgorod, Russian news agencies reported on Sunday, citing law enforcement sources.

"Two members of an illegal armed gang have been liquidated in a special operation," TASS state news agency quoted a source saying, while a law enforcement source told RIA Novosti: "They have shot dead two (people) suspected of terrorism."

There was no immediate official confirmation of the reports.

The regional branch of the FSB security service told Interfax news agency that "until urgent investigative steps are finished, we will not comment. Later we plan an official press release."

Local media posted photographs from social networking sites apparently showing two bodies lying on the ground close to a car with doors open, as vehicles and security officers block the nearby road in a suburb of the sprawling industrial city on the Volga.

A local resident told Interfax that he heard shots in the morning between 8 and 9 am and security forces told people living in the residential area not to leave their homes.