Ukraine's acting President Oleksandr Turchynov says Russia "is at war" with his country, and that local and institutional support for Moscow is a "colossal problem" in eastern Ukraine.
Speaking on May 4 with Ukraine's Channel 5 TV, Turchynov accused Moscow of trying "to destabilize the situation completely" in eastern and southern Ukraine.
He said Odesa is "one of the Russian Federation's main targets."
But he added that "patriotic" Ukrainians have blocked the efforts of "local provocateurs and separatists" whom he accuses of "organizing" violence in an attempt to bring the Odesa "to its knees."
The acting president also said pro-Russian "organizers and perpetrators" of violence in Odesa during the weekend included "a lot of people with Russian passports and guest stars" from Moldova's breakaway region of Transdniester.
Turchynov said many police in eastern Ukraine are also "sympathetic to separatist groups" – making the situation in Luhansk and Donetsk dramatically different to the other regions in Ukraine.
"Russian special forces aimed to destabilize many regions in the south, east, and even the center of Ukraine. But at the same time they only achieved a real result in the east, in the Donetsk and Luhansk regions," he said.
Turchynov admitted that Kyiv's attempts to launch military operations against pro-Russian separatists in eastern Ukraine had also been slowed "first of all because there is a big number of people, let's be honest, residents of these regions, that support separatists -- or support even terrorists."
Turchynov's remarks come after street fighting in Odesa between crowds of pro-Russian separatists and Ukrainian nationalists on May 2 left more than 40 people dead.
Most of the victims died in a blaze apparently started by firebombs thrown into a building where pro-Russian demonstrators had sought refuge amid the clashes.
Ukrainian Interior Minister Arsen Avakov announced
on May 5 that 42 people detained over the Odesa violence had been transferred to detention facilities in central Ukraine.
The announcement came one day after more than 60 pro-Russian detainees were freed when a crowd of around 2,000 people attacked the police headquarters in the southern port city demanding their release, an attack that coincided with a visit by Ukrainian Prime Minister Arseniy Yatsenyuk.
During his visit to Odesa, Yatsenyuk accused Russia of engineering the violence.
In Moscow, Russian Deputy Foreign Minister Grigory Karasin said on May 4 that the events in Odesa showed that the Ukrainian authorities are unable to establish a dialogue with the pro-Russian population in the country.
Karasin said the deaths in Odesa should serve as "a warning for the entire world."