An armed man, who took a senior policeman hostage in the central Ukrainian city of Poltava on Thursday and drove off with him, has abandoned both the car and the officer and run into a forest, the police said.
It was the second hostage-taking in Ukraine in three days, Reuters said.
On Tuesday, an armed man held 13 people captive on a bus for hours before releasing them.
Police were trying to arrest a man suspected of car theft when he took out a grenade and threatened to kill one of the officers, Deputy Interior Minister Anton Gerashchenko said on Facebook.
After negotiations, the man exchanged the police officer for police colonel Vitaliy Shyyan and drove off with him in a car provided by police.
Gerashechenko and local authorities say police allowed the man to leave the town "for the safety of citizens."
"The intruder left the car in the middle of the road and ran to the forest. A special operation to detain a dangerous armed criminal is underway. The hostage was released. He is unharmed," the police said on Facebook.
The hostage-taker was identified as Roman Skrypnyk, 32, according to Ukraine's Interior Ministry. He has a criminal record (theft, fraud, production and distribution of drugs).