Foreign Affairs Minister John Baird called for "a fair and free" investigation into a series of explosions that rocked the Ukrainian city of Dnipropetrovsk Friday.

"This is a sad situation and our thoughts are with the victims and their families," Baird said in a statement. "Canada condemns these cowardly acts without reservation and supports efforts to bring those responsible to justice swiftly.

"We also strongly encourage the Ukrainian government not to use this unfortunate situation as a pretext to curtail basic freedoms like freedom of expression."

On Saturday, Ukrainian President Viktor Yanukovich promised a swift investigation into the bomb blasts 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.