Ukraine's military has confirmed that the eastern city of Lysychansk has fallen to Russian forces.
"After heavy fighting for Lysychansk, the defence forces of Ukraine were forced to withdraw from their occupied positions and lines," the army general staff said.
Earlier Russia's Defence Minister Sergei Shoigu said his forces had captured Lysychansk and taken full control of Luhansk region.
Ukraine's troops were outgunned there.
Its general staff said that "in order to preserve the lives of Ukrainian defenders, a decision was made to withdraw".
It said the Russians had multiple advantages in artillery, aircraft, manpower and other forces.
President Volodymyr Zelensky pledged that Ukrainian forces would return to Lysychansk thanks to their tactics and "thanks to the increase in the supply of modern weapons".
Earlier, the head of Russia's Chechen Republic, Ramzan Kadyrov, published video apparently showing Chechen fighters in the centre of Lysychansk.