Russia's top domestic security agency says one Russian border guard has been killed in a shootout with two men who tried to cross into Ukraine.

The FSB said in a statement Monday the two men on Saturday opened fire when the officer who approached them in a Russian village that borders northeast Ukraine. One of the men blew himself up and the other was detained. The border guard died of gunshot wounds.

The FSB did not provide any other details on the attackers, although unnamed security sources told Russian news agencies the men were militants traveling from the Middle East to Europe.

Ukraine's Border Guard Service on Monday denied reports that the men were crossing over from Ukraine, saying no such clash happened on their side of the border.