Russian-installed authorities ordered on Saturday all residents of the southern Ukrainian city of Kherson to leave the city immediately.
It was noted that the order was due to the "tense military situation."
Thousands of civilians have been leaving for days across the Dnipro River after warnings of a looming Ukrainian offensive to recapture the city, but Saturday's warning was delivered with renewed urgency.
"Due to the tense situation at the front, the increased danger of massive shelling of the city and the threat of terrorist attacks, all civilians must immediately leave the city and cross to the left (east) bank of the Dnipro!" said a statement posted on Telegram.
"Take care of the safety of your family and friends! Do not forget documents, money, valuables and clothes."
The statement said all departments and ministries of the Russian-installed administration in Kherson should also leave. It urged people to board river boats across the Dnipro.
One of the most important battles of the eight-month-old war is coming to a head near Kherson as Ukrainian forces advance along the Dnipro's west bank, aiming to recapture the city and encircle thousands of Russian troops.
Ukraine has imposed an information blackout from the Kherson front, but Russian commander General Sergei Surovikin said this week the situation in Kherson was "already difficult" and Russia was "not ruling out difficult decisions" there.
In a briefing on Saturday, the Russian defence ministry said its forces had repelled a Ukrainian attempt to break through its line of control in Kherson region. Reuters could not independently confirm battlefield claims.
Kherson is the only provincial capital that Russia has captured intact and held since its Feb. 24 invasion. The Kherson region was one of four that President Vladimir Putin said last month that Moscow was claiming "forever" as its own territory.
Putin has said he is prepared to resort to nuclear weapons if necessary to defend what Russia claims as its own lands. The declared annexation was condemned as illegal by Ukraine, its allies and the United Nations General Assembly.
