Ukraine’s President Volodymyr Zelensky says Russia has launched an assault to seize the eastern Donbas region.
Russian and Ukrainian forces clashed on Tuesday along the eastern front line, after Mr Zelensky said the battle for the Donbas had begun.
According to the BBC, Ukraine’s top security official, Oleksiy Danilov, said Russia was trying break through Ukrainian defensive positions throughout Ukraine’s east.
The offensive had been expected after Russia failed to seize Kyiv.
After its push to overrun the capital stalled, Moscow announced its military would focus instead on eastern Ukraine where Russian-backed separatists have been fighting Ukrainian forces since 2014.
Luhansk is one of the most fiercely contested regions, and on Tuesday its Governor Serhiy Hayday said it had come under attack from all sides.