Lithuania is "extremely concerned" about developments in its neighbour Belarus and the presence of Wagner mercenary group chief Yevgeny Prigozhin, the Baltic country's president said Thursday.
Following a rebellion by the mercenary group, Russian President Vladimir Putin ordered that Wagner lose its heavy weaponry, and that its fighters either join the regular armed forces or accept exile in Belarus.
The aborted mutiny was the biggest threat to Putin's rule since 1999.
"We are extremely concerned about the developments in Belarus. Prigozhin is already there... I cannot say 100 percent but it is very likely that he is already there," Lithuanian President Gitanas Nauseda said before an EU leaders' summit in Brussels.
The leader of the Baltic country, which neighbours both Belarus and Russia and will host next month's NATO summit, repeated his call for a strengthened eastern flank.
"The fighter groups or these serial killers (as) I call them... they could emerge in Belarus at any moment and nobody knows when they could turn against us," he added.
The European Union this month agreed an 11th package of penalties against Russia over its war in Ukraine, including measures aimed at clamping down on evasion of restrictions already in place.
Nauseda welcomed the "step forward" but said he expected "a 12th package of sanctions" against Russia and repeated his call for Russian atomic agency Rosatom to be "punished".