Pro-Russian armed men have taken control of Ukrainian troop carriers that were driven into the eastern Ukrainian city of Slovyansk, Reuters news agency reports.
A soldier manning one of the carriers now under the control of pro-Russian separatists said on Wednesday, that he was a member of Ukraine's 25th paratrooper division from Dnipropetrovsk, and that they had switched support to Russia.
"All the soldiers and the officers are here," he said. "We are all boys who won't shoot our own people."
Ukraine's defence ministery denied the reports of defections and said said a pro-Russian armed group had taken two of its soldiers "hostage" in the separatist eastern region of Lugansk.
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The ministry said an officer and a soldier were seized by "extremists" and taken to an unknown destination after they pulled over to repair their vehicle.
Ukraine's Prime Minister Arseniy Yatsenyuk angrily reacted to the latest developments telling his cabinet that Russia was "exporting terrorism" to his country.
"As far as I understand, the Russian Federation has a new product for export. Besides exporting oil and gas, Russia has started exporting terrorism to Ukraine," he said. "It seems like there is only one country in the world, namely Russia, that does not see that Russian groups of infiltrators are committing acts of terrorism on the Ukrainian territory."
Earlier on Wednesday, armoured vehicles bearing the Russian flag rolled through the eastern Ukrainian town of Kramatorsk and city of Slovyansk.
Dozens of armed men in camouflage were seated on top of the three vehicles as they drove through Kramatorsk accompanied by a military truck, according to Al Jazeera's Hoda Abdel-Hamid.
Associated Press news agency was also reporting that six combat vehicles flying Russian flags rolled into Slovyansk, and were "enthusiastically greeted" at pro-Russian checkpoints outside the city.
The troops on those vehicles wore green camouflage uniforms, had automatic weapons and grenade launchers and at least one had the St George ribbon - a symbol of the pro-Russian insurgency in eastern Ukraine - attached to his uniform.
While in Donetsk, at least 20 pro-Russian protesters armed with Kalashnikov rifles seized the city council building and entered the mayor's office, according to Al Jazeera's Kim Vinnell.
On Tuesday, Russian President Vladimir Putin warned that Ukraine was lurching towards a state of civil war, after Kiev began military operations in Kramatorsk and seized control of an airfield there.
The acting Ukrainian president, Oleksandr Turchynov, said on Tuesday his forces had taken the airfield in the first action of a threatened "anti-terrorist" campaign.
|Pro-Russian gunmen seize Donetsk city council building
Videos showed military jets patrolling the skies around the airfield as the general in command of Ukraine's forces told pro-Russian crowds to disperse. Ukrainian soldiers were also seen stationed around the site.
Reuters reported that airborne forces had also landed in the nearby town of Slovyansk, but were pulled back to base after meeting a hostile reception from local civilians.
The developments came a day after a deadline set by Ukraine's acting Turchynov, calling on pro-Russian separatists to lay down arms and leave occupied government offices, expired at 0600 GMT.
The separatists, many of them armed, continued to occupy government, police and other administrative buildings in at least nine cities in the country's Russian-speaking east, demanding broader autonomy and closer ties with Russia.
Russia had earlier warned Ukraine against using force, saying that could prompt the country to walk out of Thursday's talks in Geneva.
Source: Al Jazeera and agencies