Ukrainian forces are battling Russian troops on the streets of Ukraine's second city Kharkiv, according to local officials.
Regional governor Oleh Sinegubov said light vehicles had entered the city, as he urged its 1.4 million residents to stay indoors.
The advance came after missiles rained down overnight.
A nine-storey residential tower was hit, emergency services said.
The building was severely damaged and an elderly woman was killed, but rescuers said about 60 people were spared injury as they had taken refuge in the basement.
Russian troops also blew up a natural gas pipeline nearby, according to a Ukrainian state communications agency.
It comes after an oil terminal outside the capital Kyiv was attacked by missile, prompting toxic air warnings.
The massive explosion in Vasylkiv, 18 miles (30km) south of Kyiv, saw flames light up the night sky.
Those nearby were warned to close their windows - though many in Kyiv are already sheltering underground.
