Kiev (dpa) - Ukrainian President Volodymyr Zelensky explained on Wednesday that he complied with a hostage-takers's demand to promote a film about the abuse of animals because that decision led to the release of the hostages.

The hostage-taker, identified as a 44-year-old Ukrainian citizen born in Russia and previously twice convicted, including for illegal arms possession, was captured on Tuesday after a 12-hour stand-off in the north-western city of Lutsk. He has been charged with terrorism.

Zelensky said it was an "obvious step" to comply with the demand and post a short video on Facebook urging the public to watch the 2005 documentary film "Earthlings," about mankind using animals for food, pets and clothing.

"We have a result, everyone is alive ... and this is the most important value for me," Zelensky said in a statement published by his office.

Zelensky had reached an agreement with the hostage-taker that a half hour after the video message was to be posted on the social network, the attacker would release all the hostages, the statement said.

A total of 13 hostages were on the bus. Three of them - two women and a child - were initially released during negotiations with Zelensky. Then the rest were released as the attacker was captured.

"Everyone should watch the 2005 film 'Earthlings,'" Zelensky said in the six-second video, which was later deleted.

He had also posted excerpts from a Twitter feed believed to have been used by the hostage-taker, including the demand that senior officials and clergy members declare themselves to be a "terrorist."

The hostage-taker was armed with a Kalashnikov assault rifle, a handgun and a grenade. He was identified as the author of an online book, "Philosophy of a Criminal," about being incarcerated. Media reports said he is considered to be suffering from psychological problems.