According to AP news agency, Ukrainian police said that an armed man was holding about 20 hostages on the bus.
"Allarming news from Lutsk. This morning at 9:25 (local time), a man controlled the bus and took the hostage," Ukrainian President Volodymyr Zelensky said in a post, adding that measures are being taken to handle the situation without casualties.
Police have blocked the center of Lutsk, a city 400 km west of the capital Kiev. The attackers used weapons and were carrying explosives.
The attackers' motives were initially determined to stem from dissatisfaction with the regime, with a series of complaints on social media before.
Images posted by local media show bullet holes appearing on the body of the white bus with blue stripes, in addition, 3 windows were broken. Many witnesses said that the gun exploded at the scene and it was not clear whether there were any casualties or not.
