President Viktor Yanukovych on Saturday visited Ukraine's industrial heartland after a wave of blasts injured dozens of people ahead of the Euro 2012 football tournament.
The unclaimed attack came after tensions over the fate of jailed opposition leader drew calls from some European leaders to strip the ex-Soviet nation of the prestigious event ahead of the June 8 kickoff.
Yanukovych, taking personal charge of the blasts probe, held a closed security meeting at the scene and announced a two-million-hryvnia ($250,000, 190,000 euros) reward "for information that will help solve the crime."
"We must do all we can to find the criminals and establish the motives of the crime and its aim," he said at the start of the meeting, adding that investigators from neighbouring countries were also taking part.
He visited victims in several hospitals, meeting patients including a 16-year-old girl who suffered most in the blasts, his office said, adding that doctors operated on her and managed to save her sight.
"Our main task today is to prevent such a thing happening again," Yanukovych said, warning that "it's possible that we are talking about an attempt to destabilise the situation in the country."
On Saturday, 22 victims remained in hospital, with four in a serious condition, the health ministry said, putting the total number of injured at 30 as opposed to the 26 reported by the emergencies ministry.
One male victim had to have an arm amputated, a spokeswoman for the city's health department told the Interfax news agency.
The rare attacks have shocked Ukraine, which has witnessed no major acts of terror in its modern history and where political violence is rare.
"A terrorist attack in Dnipropetrovsk: who needs this?" the mass-circulated Komsomolskaya Pravda daily asked.
"A tram stop blew up into the air, and passersby bandaged the wounded," wrote the Segodnya daily. "There was panic in Dnipropetrovsk and people were weeping on the streets."
The attacks came as the nation puts the finishing touches on its preparations for Euro 2012, an event it is co-hosting with Poland and is hoping to use to showcase the strides it has made since the Soviet era.
Although Dnipropetrovsk is not a host city in the country's first major international sports event, it lies on the route of a tour the trophy will be taken on, visiting the city of one million on May 21.
Europe's football governing body UEFA has said it is confident Ukraine will be able to ensure security, although Donald Tusk, prime minister of co-host Poland, said: "This issue needs to be treated with the utmost seriousness."
The head of the Football Federation of Ukraine Grigory Surkis told AFP he believed the blasts aimed "to torpedo the tournament in Ukraine at all costs and compromise our country in the eyes of the international community."
Some suspect a political motive since Dnipropetrovsk is the home town of Yanukovych's arch-foe, the 2004 Orange Revolution leader Tymoshenko, who is serving a disputed jail term that has strained Kiev's ties with the European Union.
The blasts rang out on the same day that she publicised photographs of bruises and scratches she says were caused by prison guards forcibly hospitalising her at a local clinic against her will.
She has now been on hunger strike for more than a week and has appealed to be allowed to have treatment abroad for chronic back pain.
Tymoshenko now faces fresh tax charges that could increase her sentence to 12 years. At the latest hearing on Saturday, which she did not attend, the court ruled that she could not be tried in absentia and adjourned the case until May 21.