Four explosions have occurred in the industrial city of Dnipropetrovsk in eastern Ukraine, wounding at least 27 people. All the blasts happened within an hour.
Nine children were among the casualties.
The first two blasts happened at a busy central tram stop and near a cinema.
All the devices were apparently planted in rubbish bins.
The city is the birthplace of jailed opposition leader Yulia Tymoshenko.
The Prosecutor General's Office said the explosions were being treated as a terrorist attack.
The first blast occurred at a tram stop at 11.50am on Friday and the second was 30 minutes later next to a cinema.
The third blast followed shortly afterwards next to a park. The fourth explosion was also in the downtown area.
Dnipropetrovsk is 400km southeast of the capital Kiev.
Ukraine co-hosts the European football championships with Poland in two months.