At least two gunmen died and four were injured after a firefight that erupted in the western Ukrainian city of Mukacheve, close to the country's borders with Hungary and Slovakia.
According to Interfax News Agency, the Saturday attack allegedly involved members of the Right Sector, a Ukrainian far-right paramilitary group that has previously clashed with the Ukrainian government. The group was heavily involved in the Euromaidan protests in Kiev last year that led to the ousting of former pro-Russian president Viktor Yanukovych.
Video of the aftermath of the gunfight shows soldiers dragging the body of a man into a military vehicle, while another stands watch behind a machine gun loaded into the back of another vehicle.
Few details have emerged about the attack, but Ukrainian Prosecutor General Viktor Shokin has reportedly set up a joint investigative team to look into the incident, according to Russian news agency Ria Novosti.
Other videos and social media posts purportedly show members of Ukraine's national guard preparing to be deployed to Mukacheve, and armored trucks arriving in the city.
Russian officials and media have frequently portrayed members of the Right Sector as "neo-Nazi" radicals for their participation in the Euromaidan protests and anti-Russian violence, which was used by Russian leaders to justify the annexation of Crimea in February 2014. The Russian Ministry of Justice added the Right Sector to a list of non-commercial organizations that are banned in the country in January.
Following last year's uprising, the Ukrainian government has taken a tough stance on members of right-wing nationalist groups that have grown in prominence, introducing laws to disarm all vigilante militia groups.
As well as being an active political party, the Right Sector also has paramilitary fighters on the front lines in the country's restive east, where Ukrainian forces continue to clash with pro-Russian separatists.
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