Russian authorities announced a manhunt on Saturday after six convicts escaped their correctional facility through a secret tunnel.
Prison guards in the western Lipetsk region were alerted to their disappearance after carrying out a routine inspection.
“In general regime penal colony No. 2, an underground tunnel was discovered during a patrol of the premises,” the prison service of the Lipetsk region said.
“Immediately a count of convicts got underway, which revealed the absence of six inmates,” it added.
It did not reveal their identities, but said in a statement the suspects were “from Central Asia”.
Temporary search posts have been set up, while local law enforcement have been alerted and are in hot pursuit.
“Measures are currently being taken to track down the persons who have escaped. The perpetrators will be brought to justice,” it added.
The Lipetsk region is about 300 kilometres (190 miles) south of Moscow.
Russia has one of the highest prison populations in the world, but numbers have decreased as convicts are sent to fight in Ukraine.
Escapes are relatively rare in Russia and those that manage to break out are often caught within days.