An unidentified man Wednesday entered the Ukrainian government building and threatened to detonate a grenade inside, police said.

"I won't leave here alive, I'll go to jail for 10 years," the man seen standing at the entrance to the building said in a video released by Ukrainian media.

An AFP correspondent at the scene said that police cordoned off the area.

Interior Ministry spokesman Artem Shevchenko told AFP it was "not clear" if the grenade was real.

The man sporting a striped T-shirt and jeans was seen holding a white object that looked like a hand grenade. He shouted that the grenade was real.

In a statement, Kiev police said that negotiations with the man were ongoing.

However, it was not clear whether he made any demands.