KHARKIV, Ukraine -- Authorities say a bomb exploded in the center of the eastern Ukrainian city of Kharkiv on April 21.
It was the latest in a series of bombings in a major government-held city that is seen as a prize coveted by Russian-backed separatists.
An Opel SUV that was used by Ukrainian forces in military operations against separatists in the neighboring Donetsk region exploded at around 4 a.m.
The blast shattered windows in nearby buildings, but no casualties were reported.
There was no immediate claim of responsibility.
A series of bomb blasts have hit Kharkiv and the southern port city of Odesa in recent months, several of them targeting organizations with ties to soldiers who have battled separatists in a conflict that has killed more than 6,100 people since April 2014.
Ukrainian authorities blame the explosions on Russia and the rebels.