The Amur River near Khabarovsk has risen above seven meters, prompting the first evacuations from the eastern Russian city.
The Khabarovsk city administration said some 850 people were moved from their homes. The administration did not mention if more people would be evacuated.
Local officials predicted on August 22 that the river level in the Khabarovsk area could rise even higher. The local meteorological service says the level could peak at 7.8 meters by August 28.
On August 22, the Khabarovsk Region's acting governor, Vyacheslav Shport, spoke about the situation on Russian television.
"As of today there are about 650 houses and over 900 land allotments adjacent to buildings that have been inundated," he said. "The evacuation of citizens is proceeding in a calm manner according to schedule. We have temporary shelters prepared to accommodate about 11,500 people whom we are ready to evacuate."
The level of the Amur River is the highest since officials started keeping records some 120 years ago.
Shport also spoke about efforts to combat flooding in the city of Khabarovsk.
"Today we are proceeding with dike construction; we are pouring down [sand] along the central embankment of the city..." he said. "We are working to save historical monuments. The dikes are being worked on around the clock. The temporary barriers that we are erecting now are supposed to prevent the water from entering the city."
About 300 kilometers downstream, the river levels in Komsomolsk-na-Amur have already started rising and areas east of Khabarovsk are preparing for flooding.
The Russian government has sent military units to the region to erect barriers along the river banks and provide aid to the thousands of people whose homes and farms have been flooded.
Scores of people have been reported killed by the flooding on the Chinese side of the Amur River.
With reporting by ITAR-TASS and Interfax