In the early hours of Friday morning, they arrived and took control of two airports in the Ukrainian region of Crimea.
Here at Simferopol aiport the men carrying assault rifles and machine guns can be seen patrolling the airport grounds.
They are move freely in the control tower but appear to be allowing the airport to operate as normal.
This Simferopol resident says the armed men have not entered the passenger terminal.
(SOUNDBITE) (Russian) SIMFEROPOL RESIDENT, OLEG, SAYING:
"I am very worried, but what can I do at the moment? I don't know who they are, I don't know what it's about. My family is staying here, but I think that everything will be all right, I believe in the better."
This man is called Vladimir. He says he's a volunteer helping the "People's MIlitia of Crimea".
(SOUNDBITE) (Russian) REPRESENTATIVE OF GROUP CALLED PEOPLE'S MILITIA OF CRIMEA, VLADIMIR, SAYING:
"We are here to ensure general order. We don't want radicals com
