Ukraine's offensive to recapture an eastern city controlled by pro-Russia forces sharply escalated the crisis in the country's east and set off a clash Friday in the southern port of Odessa that police say killed 31 people.
The Kremlin said the move by Kiev's interim government effectively killed the Geneva pact aimed at cooling the unrest. But Russia says it will continue to try to halt the spiral and Kiev has limited ability to step it up.
By nightfall, Ukrainian troops and armored personnel carriers had blocked all major roads into the eastern city of Slovyansk, the center of the pro-Russia insurgency. In the city, most shops were closed and the few that were open were crowded with customers trying to stockpile food and supplies.
Acting President Oleksandr Turchynov claimed that ``many'' insurgents were killed or wounded Friday, but the offensive also underlined the military's vulnerability. Both sides said two Ukrainian helicopters were shot down by the insurgents, killing two crew members.
The Ukrainian Security Service said one was downed with a surface-to-air missile, adding that the sophisticated weapon undercut Russia's claims the city of 125,000 people was simply under the control of armed locals.
"Ukrainian security forces so far are not ready for large-scale military actions; moreover, such actions could provoke Russia's invasion,'' said Kiev-based political analyst Volodymyr Fesenko.
Russia has massed tens of thousands of troops in areas near Ukraine's border. Kiev officials claim Russia is preparing to invade and that it is fomenting the unrest in the east, where insurgents have seized government buildings in about a dozen cities in towns. Moscow denies the allegations, but Foreign Minister Sergey Lavrov has warned Russia would respond to attacks on Russian citizens or interests in the east.
Unlike eastern Ukraine, Odessa had remained largely untroubled since the February toppling of President Viktor Yanukovych, who fled to Russia. But a clash erupted late Friday between pro-Russians and government supporters in the key port on the Black Sea coast, located 550 kilometers (330 miles) from the turmoil in the east.
Police said the deadly fire broke out in a trade union building Friday, but did not give details on how it started. Earlier police said at least three people had died in a clash between the two sides.
In Moscow, Russian President Vladimir Putin's spokesman said the Ukrainian offensive ``effectively destroyed the last hope for the implementation of the Geneva agreement'' of two weeks ago that aimed