Ukraine launched an offensive against separatist forces for control of a besieged eastern city Friday, while clashes between pro- and anti-government activists in the previously calm southern port of Odesa led to a fire that police said killed 31 people.
The first serious offensive by the government in Kyiv and the dozens of deaths in Odesa sharply escalated the crisis that has led to the worst tensions between Russia and the West since the Cold war. The Kremlin said the battle for the separatist-held city of Slovyansk effectively destroyed the Geneva pact aimed at cooling the unrest in the deeply divided country.
Oleksandr Turchynov, Ukraine's acting president, said many insurgents were killed or wounded in the eastern offensive that also underlined the military's vulnerability. The military action came two days after Kyiv said it had lost control of eastern Ukraine.
Both sides said two Ukrainian helicopters were shot down by the insurgents near Slovyansk, killing two crew members, while authorities said another seven people also died: three separatist gunmen, two soldiers and two civilians.
By nightfall, Ukrainian troops and armoured personnel carriers blocked all major roads into Slovyansk, and the central part of the city remained in the hands of pro-Russia gunmen, according to Associated Press journalists inside. Most shops were closed, and the few that were open were crowded with customers stocking up on supplies.
Sporadic gunfire was heard in Slovyansk's downtown late Friday, while Russian news reports said there were armed clashes in the nearby town of Kramatorsk. There was no immediate independent confirmation of fighting.
The Ukrainian Security Service said one helicopter 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 Kyiv-based political analyst Volodymyr Fesenko.
Russia has massed tens of thousands of troops in areas near Ukraine's border. Kyiv claims Moscow 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 and towns. The Kremlin denies the allegations, but Foreign Minister Sergey Lavrov has warned Russia would respond to attacks on its citizens or interests in the east.
Unlike eastern Ukraine, Odesa had been largely tranquil since the February toppling of President Viktor Yanukovych, who fled to Russia. But clashes erupted Friday between pro-Russians and government supporters in the key port on the Black Sea coast, located 550 kilometres (330 miles) from the turmoil in the east.
Police said the deadly fire broke out in a trade union building, 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 the city of 1 million.