Ukrainian Prime Minister Arseniy Yatsenyuk has accused Russia of engineering this week's violence in Odesa that left dozens of people dead.
Speaking on a visit to the southern port city on May 4, Yatsenyuk said the violence resulted from a "well-prepared and organized action against people, against Ukraine, and against Odesa."
He also blamed security forces for failing to prevent the bloodshed.
More than 40 people died on May 2 in clashes between pro-Russian separatists and pro-Kyiv protesters.
Most of the victims died in a blaze apparently started by firebombs thrown inside the building where pro-Russia activists had sought refuge amid the street fighting.
It was the worst bloodshed in Ukraine since ousted pro-Moscow President Viktor Yanukovych was forced to flee the country following a bloody crackdown on antigovernment protesters in February.
Russia has accused Yatsenyuk's government of provoking bloodshed in eastern Ukraine with an operation to restore Kyiv's authority in a series of cities under the control of pro-Russian rebels.
Following Yanukovych's ouster, pro-Russian militants seized government buildings in a string of cities across Ukraine's mainly Russian-speaking east.
Yatsenyuk rejected the accusation, saying "The process of dialogue had begun, only it was drowned out by the sound of shooting from automatic rifles of Russian production."
Yatsenyuk has also said the Odesa violence was provoked by pro-Russia militants.
He has blamed security forces for failing to prevent the bloodshed, and promised a full and independent investigation.
The interior minister has already fired Odesa's police chief.
Ukraine's government has vowed to press ahead with an "antiterrorist" operation against pro-Russian rebels in eastern Ukraine, but there were no reports of fresh clashes on May 4.
On May 4, the Russian Foreign Ministry called on the Organization for Security and Cooperation in Europe (OSCE) and the Council of Europe to "objectively evaluate" developments in eastern Ukraine.
It accused Ukraine's government of conducting "punitive" operations in the country's east and the West of imposing an "actual information blockade" on developments.
On May 4, several hundred pro-Russian activists surrounded a police station in Odesa demanding the release of their comrades detained after the fire and fighting two days earlier.
Police has said dozens of people remain in custody over the May 2 violence.
With reporting by Reuters, AP, Interfax