Dozens of people died yesterday in Odesa, most of them in a building that was set on fire after clashes between pro-Russian activists and supporters of a united Ukraine in the southern port city.
In the worst violence to hit Odesa since the ouster of Viktor Yanukovych in February, 31 people suffocated or died by jumping out of windows after a trade union building was set on fire, police said.
Opposing parties have met before in Odessa, but so far there have been no casualties.
Earlier, police said at least four men were killed in clashes after a march of pro-Kiev protesters was ambushed. Molotov cocktails, oysters and explosive devices were thrown. Waving Ukrainian flags, wearing helmets and wielding sticks, thousands of Ukrainians took to the streets to march in support of the pro-Western authorities in Kiev. Reuters reported that some were supporters of the local football club Chernomorets.
In an attack tinged with football rivalry, pro-Russian activists, many with Metalists from Kharkiv insignia, attacked the crowd. The police soon lost control.
Local MP Dmytro Spivak told Ukrainian television that at least six young supporters of the Kiev government had been killed.
"It is absolutely clear that the pro-Russian side is very well armed, organized and that this action was planned a long time ago," he said, adding that the police did little to stop the clashes.
In the east of the country, pro-Russian separatists shot down two Ukrainian military helicopters that were participating in an operation to expel extremists from their stronghold in Slavyansk. Kiev announced that two pilots were killed and seven soldiers were wounded in an action which, as they admitted, achieved little.
The separatists said Ukrainian forces killed three of their fighters and two civilians when they stormed Slavyansk, in what Moscow described as a "criminal" attack.
Turchinov said the operation was complicated by the fact that the rebels were using human shields and were not advancing as quickly as they had hoped.
Ukraine claims that the use of rockets that shot down its helicopters is proof of the presence of Russian forces in that city. Moscow denies that its army is on the ground.
The Ukrainian Defense Ministry announced last night that two Ukrainian soldiers were killed on the outskirts of Slavyansk after pro-Russian separatists attacked their position.
The Acting President of Ukraine, Oleksandr Turchynov, said that Russian "armed saboteurs" tried to enter the country the night before last, but were prevented by Ukrainian border guards. The Russian security service denied this.
Kiev claims that Moscow supports groups in eastern Ukraine that "endanger civilians, take hostages and create an atmosphere of terror and violence."
Ukrainian forces in armored vehicles are advancing into Slavyansk, but rebels still control much of the town of 130.000.
Turchinov said that the operation was complicated by the fact that the rebels were using human shields and that they were not advancing as quickly as they had hoped.
Reuters reported that around 100 people gathered in front of the municipality building in Slavjansk yesterday, who appealed to Putin to send the army to help them.
"What can you think when the sound of a cannon makes you jump out of bed, when helicopters fly over and shoot at our people," said Tamara Voščanaja.
Putin's popularity increased after the annexation of Crimea and statements about the establishment of the former Russian empire. This Sunday, he revived the Soviet tradition of holding a May Day parade on Red Square, where marchers carried flags and hailed the conquest of Ukrainian territory.
US Defense Secretary Chuck Hagel said that Russia's actions in Ukraine have shattered the myth of European security in the post-Cold War era and that NATO allies have increased the danger by failing to fulfill their promises on military spending.
Recalling Putin's earlier warning that any "punitive operation" would be a "criminal act," his spokesman Dmitry Peskov said that is exactly what happened in Slavyansk.
"While Russia is making efforts to de-escalate and resolve the conflict, the Kiev regime is firing on civilians from military helicopters and has begun a punitive operation, effectively destroying the last hope for the survival of the Geneva agreement," Peskov said.
According to the agreement signed on April 17 by Russia, Ukraine, the US and the EU, the separatists were supposed to surrender their weapons and free public buildings in a dozen cities they occupied across the east. Since then, however, they have only tightened their grip.
Ukraine's security service said that the separatists' use of anti-aircraft missiles was proof that "trained, highly qualified foreign military specialists" were operating in the area and not "local civilians, as the Russian government says, armed only with pistols taken from hunting stores."
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