KYIV, June 27 (Reuters) - Regional authorities urged civilians on Monday to urgently evacuate the eastern Ukrainian city of Lysychansk which is being attacked by Russian forces.

"Dear residents of Lysychansk city territorial community and their relatives! Due to the real threat to life and health, we call on you to evacuate urgently," Serhiy Gaidai, the governor of the Luhansk region, wrote on the Telegram messaging app.

He said the situation in Lysychansk was "very difficult" but did not say how many civilians remained there. About 100,000 people lived in the city before the Russian invasion of Ukraine on Feb. 24.

Gaidai said earlier on Monday that Lysychansk was suffering "catastrophic" damage from shelling as Russian forces targeted the city following the fall of neighbouring Sievierodonetsk over the weekend.