By Marie-Louise Gumuchian
(CNN) -- Ukraine's prime minister visited the Black Sea port city of Odessa on Sunday, two days after a street battle between supporters and opponents of Russia ended in a deadly blaze that killed more than 40 people.
Arseniy Yatsenyuk's trip was to "meet social, political, cultural and economic leaders from the Odessa region," his office said in a statement posted on his official website.
The riot in Odessa, ending in a fire in a besieged trade union building, was by far the worst incident in Ukraine since a February uprising that ended with a pro-Russian president fleeing the country.
Forty-six people died in the bloodshed, a spokesperson for the prosecutor's office told CNN -- six were killed in the clashes, the remainder in the fire. Of those, 32 people died due to smoke inhalation, while eight were killed trying to jump out of the burning building.
Odessa, a vibrant multi-ethnic port city, has seen some support for separatists, but nothing like the riots that erupted on Friday.
Ukraine's security service blamed the unrest in Odessa on "provocateurs."
Video posted on YouTube appeared to show supporters of Kiev throwing Molotov cocktails at the building where pro-Russian separatists had reportedly taken up positions. The footage, which CNN could not independently confirm, showed people sitting on ledges trying to escape the fire and thick smoke.
The violence in eastern Ukraine pits pro-Russian separatists against Ukrainian forces and those who support the Western-backed government in Kiev.
It has escalated into a diplomatic crisis with Russia demanding an end to what it called Ukrainian aggression and Western powers accusing Moscow of funding the violence.
On Saturday, a team of international military observers seized by pro-Russian separatists in eastern Ukraine was freed, as Kiev resumed military action to tackle the pro-Moscow gunmen who have overrun the region.
Ukrainian troop carriers moved into the eastern city of Kramatorsk, where some residents reported hearing gunfire, as Ukraine's embattled new leaders launched their most intensive effort yet to try to dislodge the rebels who have reportedly seized government buildings in nearly a dozen cities and towns.
A CNN team on the outskirts of the town, which is some 16 kilometers (10 miles) south of the flashpoint city Slavyansk, saw troop carriers moving toward the city center. Amateur video posted online -- which CNN could not confirm the authenticity of -- showed burnt out buses, plumes of smoke and residents calmly observing it all.
Saturday's release of the monitors from the Organisation for Security and Cooperation in Europe resolves a major diplomatic issue for the West after separatists had abducted eight European observers in Slavyansk on April 25 and held them hostage.
However, in another challenge to Kiev, separatist leader Valeriy Bolotov in Luhansk declared a state of emergency and announced the formation of a "South-East" army for the entire region.
In a video statement aired on local stations, Bolotov also introduced a curfew, a ban on political parties, and his expectation that local law enforcement officials will take an oath of allegiance to the people of Luhansk.
"In case of not following this, you will be announced traitors of people of Luhansk and wartime measures will be taken against you," he announced.
Separatists, many of them of Russian descent, believe the government in Kiev is illegitimate, since it formed after what they call the illegal ousting of pro-Moscow President Viktor Yanukovych in February. Officials in Kiev accuse Moscow of meddling in its support of separatists.
Russia and the West squared off diplomatically over the fate of Ukraine after Moscow annexed the Black Sea peninsula of Crimea in March following Yanukovych's ouster. He was pushed from office after months of protests by people upset that he had turned away from Europe in favor of Moscow.
Russia has condemned Kiev's military action in the volatile east.
In a phone call Saturday with U.S. Secretary of State John Kerry, Russian Foreign Minister Sergey Lavrov said: "(The) punitive operation in the southeastern Ukraine plunges the country into fratricidal conflict."
Dmitry Peskov, President Vladimir Putin's spokesman, said Russia's government had received thousands of calls since Friday from people in southeastern Ukraine. The callers described the situation as "horrendous" and pleaded for Russia's involvement. "Most of the people literally demand active help from Russia," he said.
Nick Paton Walsh, Claudia Rebaza and Jo Shelley contributed to this report.
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