At least four blasts have been reported in the eastern Ukrainian city of Dnipropetrovsk.

A spokeswoman for the Emergency Situations Ministry said a total of 27 people, including nine schoolchildren, were injured in the explosions.

Officials were quoted as saying at least one of the blasts was caused by a suspected explosive device placed in a garbage bin.

A spokesman for the Prosecutor-General's Office said investigators were treating the blasts as suspected "terrorist acts."

President Viktor Yanukovych, on a visit to Crimea, called the blasts "a major challenge for the entire country."

Interior Minister Vitaliy Zakharchenko was flying to Dnipropetrovsk to investigate.

Officials said the first blast occurred at a tram stop in the center of the city, caused by a bomb in a trash bin.

At least three more blasts in crowded areas followed, including one near a railway station.

All the blasts occurred in crowded downtown areas.