The man, who took hostages on a passenger bus in Lutsk downtown on Tuesday morning, has two criminal records, the Interior Ministry of Ukraine told Interfax-Ukraine.

"The hostage taker has two criminal records," the ministry said.

Advisor to the Ukrainian interior minister Zorian Shkiriak said that the hostage taker was born in Russia in 1975 and earlier he was held criminally liable for robbery.

"Born in Russia in 1975. Now a citizen of Ukraine, he lives in Lutsk," Shkiriak said on air of the Ukraine 24 television channel.

He also said that the man was previously held criminally liable.

"He was tried and served sentence […] for a group robbery," Shkiriak said.

The Criminal Investigation Department of the National Police of Ukraine said in its Telegram channel that "the terrorist is taking mental treatment."

Ukrainian media reported referring to Lutsk residents that the man is an internally displaced person.