Pro-Russian activists attacked pro-Ukrainian activists with clubs and whips in the Crimean city of Sevastopol as thousands took to the streets across Ukraine in rival demonstrations on March 9.
The violence took place as some 200 demonstrators gathered to commemorate the 200th anniversary of poet and national hero Taras Shevchenko.
The events come against a backdrop of Russian forces' weeklong occupation of Ukraine's Crimea.
In Crimea's regional capital, Simferopol, separate rallies in support of Ukrainian unity and for joining Russia proceeded peacefully.
In the eastern city of Donetsk, former opposition leader Vitali Klitschko said that Ukraine should not be allowed to split apart amid bloodshed.
"The key priority today for all Ukrainians is to unite, to come together and to prevent provocations, prevent separatists from realizing their plans, which are partition of the country and loss of independence," Klitschko said.
Meanwhile, several thousand pro-Russian demonstrators gathered at Donetsk's Lenin Square calling for a Crimea-style referendum.
RFE/RL correspondent Tom Balmforth, said from Donetsk that the demonstrators marched to the regional administration building -- which was seized twice by pro-Russian demonstrators this past week -- where they took down the Ukraine flag outside and hoisted the Russian one. He said demonstrators chanted, "Referendum," "Russia, Russia" and, "Donetsk is a Russian city."
Plans to hold a pro-Ukrainian rally later were abandoned amid concerns of violence by pro-Russian activists.
Prime Minister Arseniy Yatsenyuk told thousands of demonstrators gathered in Kyiv to commemorate Shevchenko that Ukraine would not cede "a single centimeter" of its territory to Russia.
"This is our land, our parents and grandparents spilled their blood for this land," Yatsenyuk said. "We will not give up a single centimeter of Ukrainian land. Let Russia and Russian President [Vladimir Putin] know this."
Yatsenyuk later announced he would go to Washington this week to discuss the standoff with Russia over Crimea. U.S. Deputy National Security Adviser Tony Blinken told NBC television that President Barack Obama will meet with Yatsenyuk at the White House on March 12.
Addressing thousands on Kyiv's Independence Square later on March 9, Mikhail Khodorkovsy -- a fierce critic of Russian President Vladimir Putin who spent a decade behing bars before his release in December -- accused Russia of complicity in the police violence that claimed more than 100 lives last month during protests against Ukraine's ousted President Viktor Yanukovych.
Russia, meanwhile, is tightening its military grip on Crimea.
Ukraine's State Border Service said Russian forces took control of a Ukrainian border guard post in western Crimea early on March 9. It said Russian forces now controlled 11 border guard posts in Crimea.
The pro-Russian authorities in Crimea have called a 16 March referendum to split from Ukraine and join Russia.
Russian forces began deploying to Crimea within days of Yanukovych's flight from the country.
Yanukovych was toppled after three months of protests against his decision to spurn an association and free-trade agreement with the European Union for closer ties with Russia.
U.S. Secretary of State John Kerry, in his latest telephone call with Russian Foreign Minister Sergei Lavrov on March 8, warned that steps to annex Crimea to Russia would close any space for diplomacy.
Putin has said Russia has the right to protect Russian interests and ethnic Russians in Crimea.
Putin, in telephone calls with German Chancellor Angela Merkel and British Prime Minister David Cameron on March 9, defended the decision of the pro-Russian Crimea authorities to hold a referendum as legitimate.
Based on reporting by RFE/RL Ukrainian Service correspondent Anton Shulga, RFE/RL correspondent Tom Balmforth in Donetsk, and reporting by AFP, Reuters, and BBC