International pressure is mounting on Russia to find a solution with Ukraine over the crisis.

NATO says it's stepping up its cooperation in Ukraine but reviewing "an entire range" of cooperation with Russia.

Earlier hundreds of Pro-Russian demonstrators stormed a government building in Donetsk, hours after they were thrown out by police.

Meanwhile - a UN diplomat has been threatened by armed men in eastern Ukraine.

It's understood Robert Serry was accosted outside a naval headquarters and warned he should "leave Crimea".

Sky reporter Hannah Thomas Peter - who's outside the UN building in New York says the incident is seen as 'extremely serious'.

The US secretary of state says there are a "number of ideas on the table" to resolve the crisis in Ukraine.

He's just been speaking in Paris, where he's held meetings with Russian, Ukrainian, British and French foreign ministers.

John Kerry's renewed his call for Russia to call troops back from Crimea: