A series of blasts have rocked the Ukrainian city of Dnipropetrovsk, injuring 27 people, including nine teenagers, in what authorities believe was a terrorist attack.
Top law enforcement officials rushed to the city, 400 kilometres (250 miles) south-east of Kiev, to investigate but there was no immediate claim of responsibility. The violence undermined Ukraine's security just weeks before it co-hosts the European soccer championships in June.
Many Ukrainian officials called the blasts terrorist attacks, including Deputy Prosecutor General Yevgeny Blazhivsky, and President Viktor Yanukovych vowed to investigate and punish the perpetrators.
The opposition party led by jailed former prime minister Yulia Tymoshenko, however, suggested that Yanukovych's government may have organised the blasts in order to deflect the world's attention from Tymoshenko's imprisonment and reported abuse in prison.
The first of four explosions rocked a tram stop shortly before noon, injuring 13 people. The bomb was planted in a rubbish bin. The second bomb, also planted in a rubbish bin, went off about 40 minutes later near a cinema and a trade school, injuring two adults and nine teenagers. A third blast in the city centre wounded three people and a fourth, also in the centre, caused no casualties.
Deputy parliament speaker Mykola Tomenko, who is member of Tymoshenko's party, suggested the blasts were orchestrated by the government to quiet Western criticism of the Tymoshenko case.
Tymoshenko, 51, the country's top opposition leader, is serving a seven-year prison term on charges of abuse of office in a case harshly criticised by the West as politically motivated. She and Yanukovych are bitter rivals.
Tymoshenko has been on a hunger strike for a week to protest at the alleged prison abuse. She claims guards punched her in the stomach and twisted her arms and legs.
Prison officials deny mistreating Tymoshenko. But photos taken by Ukraine's top human rights official, Nina Karpachova, of Tymoshenko in bed in her jail cell show splotches on her abdomen and lower arm.
Tymoshenko's daughter Eugenia said her mother is very weak after refusing food for seven days and fears that she will be force-fed by prison officials. The European Union has expressed alarm over the investigation and Germany has pressed Ukraine to urgently treat Tymoshenko and investigate the beating allegations.