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A Ukrainian flag is flying on top of the government headquarters in Donetsk after pro-Russian demonstrators were evacuated from the building by police earlier today.
Ukraine's top security official said he hope the crisis in the Crimea region could be resolved through dialogue.
Andriy Paruby, Secretary of Ukraine's Security and Defence Council, said the situation was calmer today.
He said Russian troops had not made any new military gains overnight in Crimea, but said the danger now was the threat of pro-Russian protesters taking over government buildings inside eastern and southern Ukraine.
Police in Donetsk have evacuated pro-Russian demonstrators from the government headquarters in the city of Donetsk, where they have been since Monday.
Riot police evacuated the building this morning, after demonstrators were told there was a bomb in the building and it had to be evacuated, the protesters said. The Ukraine flag was raised over the government headquarters, replacing the Russian flag hanging put their by protesters.
A relatively small group of protesters, approximately 150 people, remain outside the building along with around the same numbers of police. The Russian flag now flies in the front yard of the building.
Protest leader Pavel Gubarev called on Putin to send troops into the city to "protect" the people of Donetsk.
Russian forces have seized two Ukrainian defence units in Crimea, news agency Interfax reports citing a military source.
However, the Ukrainian military was unable to confirm this to Reuters.
The flag of Ukraine was raised over the government headquarters in the city of Donetsk, where a Russian flag has stood since Saturday, according to witnesses.
Police also said they have have evacuated the building, which has been occupied since Monday by pro-Russian demonstrators.
Ukraine's acting Prime Minister Arseniy Yatsenyuk said Russian "aggression" is having an extremely negative effect on Ukraine's economy.
Vladimir Putin may be "pulling back" from the Ukraine in fear of a repeat of the Bosnian war in the early 1990s, a former senior diplomat to Moscow told Daybreak.
Charles Crawford urged caution and said Putin was "not necessarily as powerful as the West" in terms of the Ukrainian crisis.
"Part of what makes a difference is what I call intensity, and the Russian's really care a lot about Ukraine, but as your correspondent just said, the Ukrainians really care about the Ukraine.
"You can't be sure if Russia over-presses this they will not end up in a really bad brother against brother battle."
The toll of the 1992-95 Bosnian war lingered over the region, Mr Crawford said: "We all know from families, if families start fighting it gets really painful, as we saw in the Balkans, so that is a good place to avoid."
He added: "My sense is Putin is just pulling back from that a little bit."
A Ukrainian soldier has been pictured speaking to his daughter through gates, as troops, in what appear to be Russian military uniforms, continued to surround military bases in Crimea.
The poignant moment was captured inside the Sevastopol tactical military brigade base in Crimea.
Tensions remain high in the region, with troops loyal to Russia firing warning shots in a bid to stop advancing Ukrainian soldiers who were protesting against the occupation.
Russian and Ukrainian soldiers were involved in a tense stand-off in Crimea today as the diplomatic conflict between Russia and the US over the crisis was stepped up.
Russian president Vladimir Putin said he would consider using force as a "last resort", and claimed the uprising in Ukraine was a "unconstitutional coup", while US President Barack Obama accused Russia of violating international law.
ITV News' Europe Editor James Mates reports from Crimea:
A Ukrainian army major has told ITV News today's tense stand-off in Crimea was designed to show Russia that Ukraine should be respected amid the ongoing tension in the region.
Chanting the national anthem, Ukrainian troops marched towards the Belbek air base before the Russian guards in control of the area fired warning shots in a bid to stop them progressing.
Despite eventually being ordered to return to their base after a five hour stand-off, Major Vladyslav Kardash told Europe Editor James Mates that "at least they know to respect us":
Latest ITV News reports
Pro-Russia activists recaptured administrative headquarters in the Ukrainian city of Donetsk and flew the Russian flag from its roof.
ITV News' Europe Correspondent describes the tense atmosphere surrounds a central government building in Donetsk .