Russian operatives are now in Kiev, Ukraine officials have confirmed in a tweet, BBC reported.
Ukraine's Defence Ministry said "the enemy" were in the district of Obolon, about 9km (5.5miles) north of Kiev's parliament in the city centre, the report said.
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!"
Earlier, the Ukrainian army said armed forces are engaged in fighting in the outskirts of the capital Kiev in Dymer and Ivankiv, where a large number of Russian armoured vehicles have advanced, BBC reported.
Ukrainian armed forces said forces "continued to resist" Russian forces northwest of the capital. The post added that troops had destroyed a bridge on the border of the Teteriv River to impede the further advancement of Russian forces, BBC reported.
It added that troops were still holding on to an airfield on the outskirts of the city - which could become a springboard for the Russian army into Kiev if Russian troops were to seize it.
Fighting has seemingly intensified in the capital city of Kiev as Russian forces advance, with reports of several explosions, gunfire, and missile strikes being heard in or around the city early on Friday, BBC reported.
A Ukrainian interior ministry official claimed that a Russian aircraft has been shot down over the Darnytskyi district of Kiev, although these reports are unconfirmed
Fighting is also raging at an airfield on the outskirts of Kiev, and it could become a springboard for the Russian army into Kiev if its troops seize it
Ukraine's Deputy Defence Minister says Russian forces could enter the area just outside Kiev later today.