ODESSA, Ukraine - Thousands of pro-Russian protesters attacked Odessa's police headquarters on Sunday, days after deadly clashes and a fire there killed dozens of their comrades in what Kiev charged was a Russian plot to "destroy Ukraine".
The unrest in the southern port city threatened a new front in the Ukrainian government's battle against pro-Moscow militants, with an expanded military operation under way in the east against gunmen holding more than a dozen towns.
However, in a potentially significant diplomatic move on Sunday evening, the Kremlin announced that the head of the Organisation for Security and Cooperation in Europe (OSCE), Didier Burkhalter, will visit Moscow on Wednesday for talks on the crisis.
The meeting was announced following a phone call between Russian President Vladimir Putin and German Chancellor Angela Merkel, who later said Russia and the OSCE would discuss setting up a national dialogue in Ukraine.
"Putin and Merkel stressed the importance of effective international action -- especially by the OSCE -- in reducing the tensions in Ukraine," Russia said in its statement.
Earlier, Ukraine's Prime Minister Arseniy Yatsenyuk accused Russia of executing a plan "to destroy Ukraine and its statehood".
He was in Odessa to observe mourning for the 42 people who died there in clashes and the fire on Friday -- most of them pro-Russian militants.
The unrest shaking the Black Sea city of one million people, he said, aimed "to repeat in Odessa what is happening in the east of the country".