Fears of gas war between Russia and Ukraine grow

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 prospect of a new gas war between the two neighbouring countries drew closer at the weekend as the government in Kiev said it would refuse to pay for gas at a new, inflated price set by Gazprom last week. The dispute comes as tensions in eastern Ukraine remain high, with pro-Russian protesters in two cities storming government buildings on Sunday.

In Kiev, interim prime minister Arseniy Yatsenyuk told the cabinet over the weekend that the new price for gas was unfair and Ukraine would not pay it.

"Russia has not managed to grab Ukraine through military aggression, so now they are pursuing a plan to pressure and grab Ukraine through gas and economic aggression," said Yatsenyuk. He said that Ukraine would continue buying gas at the "acceptable market price" of $268 (£162) per 1,000 cubic metres.

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.