Russia fans the flames as aircraft cross into Ukraine
Kiev protests to Moscow as UN convenes emergency session
Russian military helicopters crossed into Ukraine and were flying towards Crimea last night as the confrontation over the crisis-torn region took a dramatic new turn.
The UN Security Council was preparing to convene an emergency session on the escalating crisis at the request of the government in Kiev, which warned that its territorial integrity was being threatened.
President Obama warned Russia that there will be costs if the country intervenes militarily in Ukraine.
Mr Obama said the US is deeply concerned by reports of military movements by Russia inside Ukraine.
He said any violation of Ukraine's sovereignty and territorial integrity would be destabilising. He said it would violate Russia's commitment to respect Ukraine's borders and would invite global condemnation.
Speaking at the White House, he said the US stands with the world community to affirm there will be costs if an intervention takes place.He spoke at the end of a day in which Russian troops and armour fanned out across Crimea, seizing two airports and other key installations in an apparent bid to assert Moscow's dominance over the region.
The Ukrainian foreign ministry said it had officially protested to Moscow over the "violation of Ukraine's air space" after at least 10 Russian helicopters crossed the border.
In a statement, the ministry asked for the "immediate return" of soldiers and equipment to their bases.
Despite "grave" warnings from America not to intervene, soldiers and unidentified armed men deployed on Crimea's main roads, and occupied key positions within ports and the region's main television station.
Although no shots were fired and there were no reported injuries, Arsen Avakov, the new Ukrainian interior minister, said the sudden and unannounced Russian deployment amounted to a "military invasion and occupation" of his country's territory.
The Kremlin's confrontation with Ukraine's post-revolutionary government appeared to be entering a new and more dangerous phase as airspace over Crimea was closed to civilian flights. Simferopol International Airport, serving the regional capital, announced that all services from Kiev were suspended until at least 6.30pm today.
Under the Budapest Memorandum of 1994, Russia is bound to "refrain from the threat or use of force against the territorial integrity or political independence of Ukraine".
In a day of dramatic developments, UK prime minister David Cameron spoke by phone to President Vladimir Putin to stress that "all countries should respect the territorial integrity and sovereignty of Ukraine". Britain and America are also signatories to the Budapest Memorandum. Downing Street said that Mr Putin had "agreed" with the prime minister.
Russia's Black Sea Fleet maintains a garrison of 25,000 military personnel inside Crimea at a base in the Crimean port of Sebastopol, which Moscow leases from Ukraine.
The Russian foreign ministry confirmed that "armoured vehicles" from this base were moving within Crimea in order to protect what it called "fleet positions". The ministry added that Ukraine's government had been given a "note" to this effect.
However, there had been no "bilateral consultations" because events in Crimea were the "result of recent internal political processes in Ukraine".
In Kiev, the defence and interior ministries both declined to comment. A spokesman for Ukraine's National Security Council said there was "no information" on whether this body had considered the situation in Crimea.
Meanwhile, deposed president Viktor Yanukovych appeared in public in Russia for the first time since fleeing Kiev. He described himself as the "elected president" of Ukraine and declared the "coup" had been "illegal". (© Daily Telegraph, London)