- Ukraine's acting President Oleksander Turchynov has accused Russia of deploying troops to Crimea and trying to provoke Kiev into "armed conflict"
- It comes amid unconfirmed reports that Russian planes have flown hundreds of troops into the region
- Armed men have blockaded airports in Crimea, Ukraine's only Russian-majority region and home to Russia's Black Sea Fleet
- Russia has denied involvement. President Vladimir Putin said sides had to stop "a further escalation of violence"
- US President Barack Obama warns Russia that "there will be costs for any military intervention in Ukraine" All times GMT
- At a news conference in Russia, Ukraine's ousted President Viktor Yanukovych says he is against any outside military intervention
- Yaroslav Lukov
- Alastair Lawson
- Patrick Jackson
- Kerry Alexandra
Welcome to our live page on the developing crisis in Crimea - Ukraine's only Russian-majority region and the home of Russia's Black Sea fleet.
Men in Russian military uniforms are blockading a military airport in the Black Sea port of Sevastopol. Meanwhile, men in military uniform without national insignia are patrolling an airport in the Crimean capital Simferopol.
Ukraine's newly appointed Interior Minister Arsen Avakov said in a Facebook post that the Belbek international airport in Sevastopol is blocked by military units of the Russian navy, calling it a "military invasion and occupation.''
The Interfax news agency reports that Russian servicemen wearing helmets and armoured body protection and backed by armoured personnel carriers, have taken up position on the perimeter of a military airport at Sevastopol. The agency quoted military sources in the region as saying that they had gone to Belbek military airport to stop "fighters" flying in.
Russian President Vladimir Putin has also ordered his government to continue talks with Ukraine on economic and trade relations and to consult foreign partners including the IMF and the G8 on financial aid, a statement on the Kremlin's website said. It also said Putin has ordered the government to consider a request from Crimea for humanitarian aid.
It is not the only crisis facing the new Ukranian government: its currency, the hryvnia, has slumped to an all-time low. The IMF has said it is ready to step in and will send a team in the coming days to assess the economic situation, but Ukraine's finance ministry has warned it needs help urgently - and 35 billion dollars over the next two years to avoid defaulting on its debt.
Julia Smirnova, Die Welt Reporter
tweets: Road to Sevastopol airport blocked by armed people
08:00The BBC's Daviel Sandford
tweets: Simferopol airport now. Armed men still here.
An armed man in a uniform without an insignia patrols at the airport in Simferopol.