DNIPROPETROVSK, Ukraine (Reuters) - Ukrainian President Viktor Yanukovich on Saturday promised a swift investigation into Friday's bomb blasts in the city of Dnipropetrovsk that injured 30 people just weeks ahead of the European soccer championship which Ukraine co-hosts.
Four bombs planted in trash bins in various downtown locations exploded at short intervals in the city of 1.3 million on Friday afternoon, in what prosecutors said was an "act of terrorism".
"We understand well that we must find the criminals as soon as possible and they must be punished," Yanukovich said after meeting top law enforcement officials in Dnipropetrovsk where he arrived on Saturday.
"We must understand what motivations and goals this crime had."
Yanukovich said city authorities would pay 2 million hryvnias ($250,000) for any information that would help find the bombers.
The president and other officials declined to say what direction the investigation was taking.
The attack, a rare event in the peaceful ex-Soviet republic, has unsettled authorities who are preparing to host the Euro-2012 soccer championship together with Poland.
Dnipropetrovsk, an important industrial and technological hub and the birthplace of many of Ukraine's political elite, is not a championship venue itself. It is located about 150 miles away from Donetsk which will host several games.
The bombings have also added to political tension in Ukraine, already high following last year's conviction of Yanukovich's opponent, former prime minister Yulia Tymoshenko, on abuse-of-office charges and a fresh tax evasion trial against her.
The government and the opposition have traded accusations of seeking to exploit the blast for political purposes.
In Dnipropetrovsk, where regular police have been reinforced by interior troops and large-scale public gatherings have been barred, many were recovering from the shock.
"I live in Israel and such explosions are not new to me but I was shocked to see a familiar picture here: a blast-hit tram and bloodied people," said 50-year-old Alexander Mogilyev.
Ukraine's healthcare ministry said in a statement on Saturday 22 people were still in hospital, three them in grave condition.
(Reporting by Pavel Polityuk; Writing by Olzhas Auyezov; Editing by Sophie Hares)