Russian operatives are now in Kyiv, Ukraine officials have confirmed in a tweet.
Ukraine's Defence Ministry said "the enemy" were in the district of Obolon, about 9km (5.5miles) north of Kyiv's parliament in the city centre.
They've encouraged locals to make Molotov cocktails to fight back, while also advising others to seek shelter.
"Peaceful residents- be careful. Do not leave the house!"
Our correspondents in Kyiv earlier reported hearing gunfire although they add it is impossible to know what it signifies at this point. They say they can now hear louder explosions too.
Source: BBC