A suicide bomber detonated himself on Tuesday at the door of the regional parliament of Russia's North Caucasus republic of Chechnya, killing two people, the RIA Novosti news agency reported.
Two or three of his accomplices broke into the parliament and began shooting, said an unnamed law enforcement source.
Shots were heard starting from 09:00 a.m. Moscow time (0500 GMT). Currently the clashes inside the parliament building have been over, but sporadic shots could still be heard from the scene.
To date no final casualties were available.
The area has been blocked with all personnel evacuated, said the source, adding that an special operation, led by Chechen leader Ramzan Kadyrov, was underway to eliminate the insurgents.
Earlier, the Interfax news agency reported, quoting an unnamed law enforcement source, that some shots were heard in the parliament, killing unspecified number of people.
Russian Interior Minister Rashid Nurgaliyev, who was currently in the regional capital of Grozny, has been informed about the incident, said the source.
Riot police have rushed to the scene where the shooting continued, said the source.
The incident has so far not been officially confirmed.
Violence is common for the mainly Muslim North Caucasus republics of Chechnya, Dagestan and Ingushetia with militants frequently assaulting police officers and authorities.
Moscow has vowed to bring stability to the region via improving social services, raising pensions and salaries as a measure to tackle corruption and terrorism infiltration.