At least three explosions have been reported in the Ukrainian city of Dnipropetrovsk, injuring more than 15 people, according to reports.
Some local news outlets reported as many as eight explosions hit the city, but that number was impossible to confirm.
Russia Today claimed that four explosions had occurred in the city, and that as many as 27 people had been hurt.
Traffic reportedly "ground to a halt" in the city as people attempted to flee without knowing where the next explosion would occur.
According to Radio Free Europe, the first blast occurred at a tram stop.
"Between three and five people who were on a tram have been injured," a police spokesman told the Reuters news agency. "So far, we know it was an explosive device."
The report claimed that the explosion was caused by a device placed in a rubbish bin, injuring five.
Around an hour later another blast hit a train station, injuring seven. A third blast was also reported.
It cannot be confirmed what caused the blasts.
Ukraine will host the Euro 2012 football championships in June.
Dnipropetrovsk is a large city in the central-south of Ukraine, and has a population of more than 1m people.
View Dnipropetrovsk, Ukraine in a larger map