Ukrainian government forces fought gun battles Monday with pro-Russian militia in the separatist-controlled eastern Ukrainian city of Slovyansk, a day after pro-Russian protesters stormed the police station in the southern city of Odessa.
Russia's Interfax news agency quoted a separatist source in Slovyansk as saying that 20 or more pro-Russian militants had been killed in the fighting.
Local media reported Monday that Ukrainian forces recaptured a television tower outside of Slovyansk.
On Sunday in Odessa, hundreds of pro-Russian militants used a battering ram on one entrance to the police station before pushing their way in through a garage. Authorities freed more than 60 of the 150 people arrested two days earlier during clashes that led to a fire which killed 42 mostly pro-Russian activists.
Ukraine's acting Prime Minister Arseniy Yatsenyuk visited the port city Sunday, declaring Russia is seeking to destroy Ukraine by engineering clashes in eastern Ukraine and now Odessa. He accused Moscow of engaging in "well-planned provocation" against the interim Kyiv government.
Ukraine says it will continue pressing its military offensive against pro-Russian separatists in eastern Ukraine, while the Kremlin reported receiving thousands of calls for help from the region's Russian-speaking citizenry.
Ukraine's acting Interior Minister Arsen Avakov said Sunday that troops had recaptured a television tower and government buildings from rebels in Kramatorsk, a town near Slovyansk.
Ukraine's National Security and Defense Council chief Andriy Parubiy said Sunday an anti-terrorist operation will be carried out in towns beyond Slovyansk and Kramatorsk.
In Moscow, a Kremlin spokesman (Dmitri Peskov) said Russian President Vladimir Putin had not yet decided how to respond to the offensive, or to the deaths in Odessa.
Russia has at least 40,000 troops and armor massed on its border with Ukraine, and the Kremlin says it reserves the right to enter the country to protect ethnic Russians.