Last Updated May 6, 2014 6:08 AM EDT
DONETSK, Ukraine -- Ukraine's Interior Minister said Tuesday that 30 pro-Russian insurgents were killed during government operations to expunge anti-government forces in and near a town in the east.
Arsen Avakov said on his Facebook page Tuesday that four government troops also died and another 20 were injured during fighting in Slovyansk.
In Donetsk, a major city some 70 miles south of Slovyansk, flights from the local airport were suspended Tuesday.
A display board at the Donetsk airport showed international flights had been cancelled and only outbound flights to the capital, Kiev, were still in operation. The airport said on its website that the cancellations followed a government order. It was not immediately clear Tuesday morning how long the suspension was due to remain in effect.
Avakov said Monday that pro-Russia forces in Slovyansk, a city of 125,000, were deploying large-caliber weapons and mortars in the region and there were injured on both sides. Government troops were facing about 800 insurgents, he said.
Ukraine is facing its worst crisis in decades as the polarized nation of 46 million tries to decide whether to look toward Europe, as its western regions want to do, or improve ties with Russia, which is favored by the many Russian-speakers in the east. Dozens of government offices have been seized, either by armed insurgents or anti-government crowds, over the past several weeks.
The goals of the pro-Russian insurgency are ostensibly geared toward pushing for broader powers of autonomy for the region, but some insurgents do favor separatism.
Leaders of the anti-government movement say they plan to hold a referendum on autonomy for eastern regions on May 11, although visible preparations for the vote have to date been virtually negligible.
The Russian Foreign Ministry has put the blame on the unrest squarely on Kiev, which it says "stubbornly continues to wage war against the people of its own country." The ministry has urged what it called the "Kiev organizers of the terror" to pull back their troops from the east and hold peaceful negotiations to resolve the crisis.
Earlier Monday, Ukraine sent an elite national guard unit to the southern port of Odessa, desperate to halt a spread of the fighting.
The government in Kiev intensified its attempts to bring both the Donetsk and Odessa regions back under its control, but seemed particularly alarmed by the bloodshed in Odessa. It had been largely peaceful until Friday, when clashes killed 46 people, many of them in a government building that was set on fire.
CBS News correspondent Clarissa Ward reported that tension was also mounting in Luhansk, a city just 20 miles from the border with Russia, where pro-Russian insurgents were fortifying defenses around their encampment in the center of town -- worried they could be next on the list for the Ukrainian military's offensive.
Retired coalminer and local insurgent commander Petrov Nikolaivich told Ward he didn't want Luhansk to become part of Russia, but insisted a referendum must be held to determine whether Donetsk and Luhansk should become independent republics.Asked why he felt a referendum was so important, Nikolaivich told CBS News it was needed to safeguard "freedom and faith... and the Fatherland."
That referendum is currently scheduled for Sunday, but Ward noted that with the security situation in the region so tenuous and moving around it so difficult, it was hard to fathom how such a vote could happen. She said it wasn't even clear whether ballots had been printed for the touted vote, or if it was really more of a symbolic gesture of defiance against the Ukrianian presidential elections scheduled to take place later this month.
The loss of Odessa -- in addition to a swath of industrial eastern Ukraine -- would be catastrophic for the interim government in Kiev, leaving the country cut off from the Black Sea. Ukraine already lost a significant part of its coastline in March, when its Crimean Peninsula was annexed by Russia.
Compared with eastern Ukraine, Odessa is a wealthy city with an educated and ethnically diverse population of more than 1 million. Jews still make up 12 percent of the population of the city, which once had a large Jewish community.
"The people of Odessa are well-educated and understand perfectly well that Russia is sowing the seeds of civil war and destabilization in Ukraine," said Vladimir Kureichik, a 52-year-old literature teacher who left Crimea after it became part of Russia.
The White House said it was "extremely concerned" by the violence in southern Ukraine.
"The events in Odessa dramatically underscore the need for an immediate de-escalation of tensions in Ukraine," said spokesman Jay Carney. He suggested Russia still must follow through with its part of a diplomatic deal aimed at defusing the tensions.
Odessa had been largely tranquil until Friday, when pro-Ukrainian demonstrators fought back after being attacked by pro-Russian groups.
"We feel ourselves to be residents of a free city, Europeans," said Denis Sukhomlinsky, a 34-year-old businessman who took part in the clashes. "We don't need the Russian iron hand or the dictatorship of (President Vladimir) Putin."
Pro-Russia activists, however, echo Putin in describing the region as historically part of Russia. Nearly 30 percent of Odessa's residents identify themselves as Russian.
"We will not become the slaves of NATO and the European Union, and will fight to the end," said Vyacheslav Khrutsky, 45.
Pro-Russia activists gathered at a funeral for a regional member of parliament, Vyacheslav Markin, who died two days after the fire from his burns. Markin was known for speaking out against the Kiev government.
Activists shouted "Hero! Hero!" and vowed to avenge him.
The city remained calm, however, and Ukrainian flags flew all over the city - unlike in the east, where pro-Moscow groups have replaced them with the Russian tricolor.