Terrorists are being blamed for a series of blasts in eastern Ukraine Friday that left at least 27 people injured.
Nine young people were among those hurt in four explosions in the city of Dnipropetrovsk, about 250 miles southeast of Kiev.
"This is yet another challenge for us, for the whole country," President Viktor Yanukovych said. "We will think of how to respond to this properly."
Political tensions in Ukraine are high as the country gears up for parliamentary elections in October. Opposition lawmakers suggested the current government may be behind the series of blasts.
Officials said the first blast, from a bomb planted in a trashcan, rocked a tram stop shortly before noon, injuring 13 people .
The second bomb, also in a garbage bin, was detonated 40 minutes later near a movie theater and trade school, injuring two adults and nine teenagers.
A third blast in the city center wounded three, and no one was harmed in a fourth explosion nearby.
The attacks come only six weeks before the European soccer championships that Ukraine will co-host.