Residents of the besieged east Ukrainian city of Lysychansk have been ordered to leave by the local governor as Russian forces push forward.

Serhiy Haidai, governor of Luhansk region, told people to evacuate immediately because of the "real threat to life and health".

The order went out just a day after Ukraine confirmed the fall of the nearby city of Severodonetsk.

The region is Russia's military focus four months after it invaded Ukraine.

Since withdrawing from the area around the capital Kyiv in early April, the Russian military and their separatist allies have been trying to drive Ukrainian government forces out of Luhansk and the neighbouring region of Donetsk, which together make up the Donbas industrial belt.

Weeks of ferocious artillery barrages have devastated urban and rural areas, leaving an unknown number of people dead and injured.

Lysychansk, a city similar in size to Severodonetsk on the other side of the Siversky Donets river, had a population of 95,000 before the current fighting.

"The situation in the city is very difficult," Governor Haidai wrote on Telegram. "Save yourself and your loved ones. Take care of the children."

The Russian military says it killed 14 "mercenaries" from Georgia and a "number of European states" 3km (1.8 miles) from Lysychansk on Sunday. The report could not be verified independently.