Russia on Saturday said it had evacuated almost 4,500 people in the Orenburg region in the southern Urals due to flooding after a dam burst.
Emergency services worked through the night after a dam burst in the city of Orsk, near the border with Kazakhstan, on Friday.
The press service of the Orenburg governor said "4,402 people, including 1,100 children" had been evacuated and more than 6,000 homes were affected by the flooding after torrential rain.
President Vladimir Putin ordered Emergency Situations Minister Alexander Kurenkov to the region, a Kremlin spokesman said late Saturday.
Authorities also opened a criminal case for "negligence and violation of construction safety rules" over the burst dam, which was built in 2014.
Authorities said the situation was difficult throughout the region, warning of a dangerous water level on the Ural river in the main city of Orenburg.
The mayor of the city of half a million people, Sergei Salmin, said authorities would forcibly evacuate people from flooded zones if necessary.
He said the water level of the Ural river had risen to dangerous levels and will rise further.
"The situation leaves you no choice. At night, the river can reach a critical level," he said. "I call on everyone in the flooded zone to leave their houses immediately.
"There is no time for convincing," he added, saying that "those who refuse to leave the danger zone voluntarily, we will forcibly evacuate with the help of police officers".
Kazakh President Kassym-Jomart Tokayev said the floods were one of the worst natural disasters in Kazakhstan in 80 years.
He called for authorities in the Central Asian country to be ready to help those affected.
Russian emergency services published images of rescue workers going through villages on boats and hovercrafts.
Several regions in the Urals and western Siberia have been affected by floods since the start of spring.