Ukraine: President calls emergency meeting over protests
Ukraine's acting president has called an emergency security meeting in response to pro-Russian protests in three eastern Ukrainian cities.
Olexander Turchynov cancelled a visit to Lithuania to deal personally with the unfolding events, his office said.
Protesters stormed government buildings and called for a vote on independence in Donetsk, Luhansk and Kharkiv.
The unrest comes amid tensions between Russia and Ukraine over Russia's annexation of Crimea.
The move, condemned as illegal by Kiev and the West, followed the ousting of Ukraine's pro-Moscow President Viktor Yanukovych in February.
Thousands of Russian soldiers are reported to have been deployed along the border between Ukraine and Russia.
Russian President Vladimir Putin has said Moscow has the right to protect the Russian-speaking population Ukraine.
Ukraine's leaders deny the country's Russian speakers are under threat and have said they will resist any intervention in their country.
Meanwhile, Nato Secretary-general Anders Fogh Rasmussen urged member nations to step up their defence spending after warning that Russia is trying to "carve up Europe into new spheres of influence."
President Turchynov called a meeting of the country's security chiefs in the capital, Kiev, after Sunday's disturbances. No further details have so far been released about the meeting.
In Donetsk, a large group of activists broke away from a crowd rallying in the main city square to attack and occupy the regional government seat.
After clashing with riot police and breaking through their lines to enter the building, they raised the Russian flag and hung a banner from the building. Protesters outside cheered and chanted: "Russia, Russia."
A spokesman for Donetsk local police, said a large group had taken part in the storming of the building.
Around 100 protesters had barricaded themselves inside, he added.
In Luhansk, police fired tear gas at dozens of protesters who broke into the local security service building in an attempt to force the release of 15 pro-Russian activists who were arrested earlier in the week and accused of plotting violent unrest.
Local news reports said at least two people had been injured in clashes, and TV pictures from the scene showed a riot policeman being taken away on a stretcher.
And in Kharkiv, several dozen people also entered the regional government building after breaking through police lines.
They waved Russian flags out of windows as a crowd outside cheered and chanted. Police officers reportedly refused to use force against the crowd and moved away from the government building after the pro-Russian supporters broke in.
Ukraine's Interior Minister Arsen Avakov accused President Putin and Mr Yanukovych - who was forced from office following months of street protests and is now living in exile in Russia - of "ordering and paying for another wave of separatist turmoil in the country's east".
In a message posted on his Facebook account, he said: "The people who have gathered are not many but they are very aggressive. The situation will be brought under control without bloodshed. But at the same time, a firm approach will be used against all who attack government buildings, law enforcement officers and other citizens."
The new administration in Ukraine has faced continuing opposition from Ukraine's Russian-speaking regions.
Writing in British newspaper The Daily Telegraph on Monday, Mr Rasmussen said that events in Ukraine had shown that "defence matters as much as ever".
The Nato chief acknowledged the "challenging" economic climate but urged the alliance's member states to "invest the necessary resources in the right capabilities".
"In the long run, a lack of security would be more costly than investing now and we owe it to our forces, and to broader society," he wrote.