Ukraine's interim government has accused Russia of staging an armed invasion in southeastern Crimea after pro-Kremlin armed men seized two airports and government buildings as Kiev calls on the United Nations Security Council to hold a meeting to discuss the developments in the region.
Two Crimean airports - the main international airport of Simferapol and a military airfield in Sevastopol - have been taken over by what the Ukrainian Interior Minister Arsen Avakov claimed to be members of a Russian Federation Fleet based in the region, according to a statement he posted on his Facebook account.
"I see what is happening as armed invasion and occupation , in violation of all international treaties and norms. This is a direct provocation of the armed bloodshed on the territory of a sovereign state," Avakov said.
The Ukrainian parliament, which voted only days ago to oust Yanukovich, has called for a UN Security Council meeting to discuss what is happening in Crimea, and urged Russia "to stop moves that show signs of undermining national sovereignty and territorial integrity" as well as "reject support for separatism in Ukraine, of any form".
EU calls for calm
Oleksander Turchynov, the acting Ukraine president who has replaced Yanukovich, told parliament he had ordered troops and police to take "all measures" needed to protect Ukrainian citizens.
In a joint statement, French, German and Polish foreign ministers, who mediated between the Yanukovich and the opposition through Ukraine's violent crisis, have urged all parties to refrain from any action endangering territorial integrity of the country.
More than 10 Russian military helicopters flew from Russia into Ukrainian airspace over the Crimea region on Friday, the Ukrainian border guard service said in a statement. It also said that Russian servicemen were blocking off a unit of Ukrainian guards in the port city of Sevastopol, where part of the Russian Black Sea fleet is based.
The Russian Black Sea Fleet issued a statement denying the accusation and insisted its forces had not seized or taken any other action at the military airport near Sevastopol, Interfax news agency reported.
Al Jazeera's Laurence Lee, reporting from Crimea, said that the civilian airport was operating normally.
"Inside the terminal building, passengers are queuing up to go to Moscow and Istanbul and all sorts of places,and that is completely normal, but in the outside, it is entirely abnormal," he said. "Throughout the morning we have seen these large groups of green camouflaged helmeted men, some are masked and others are not, in control and are coming out of the VIP block here and changing shifts."
Later in the day, Ukraine's security authorities reportedly said they regained control of the two airports.
"There was an attempt to seize the airports, but we have localised those attempts. The airports are now controlled by Ukrainian law enforcement authorities," Ukraine's National Security and Defence Council chief Andriy Parubiy said in televised remarks, according to AFP news agency.
Yanukovich's news conference
The pro-Moscow Yanukovich is expected to hold his first public appearance since his disappearance last week.
Yanukovich has apparently been emboldened by the takeover of government buildings by the armed groups. Ousted president - who fled Kiev last week following weeks of deadly protests - is due to give a press conference in Russia's southwestern city of Rostov-on-Don on Friday at 1300 GMT.
However, Al Jazeera's Rory Challands said it was still not clear who would be allowed to attend the news conference and where it would exactly be held.
Meanwhile, Crimea's pro-Yanukovich autonomous parliament has set a referendum on the region's status on May 25, according to AFP news agency, which is the same day during which the new government in Kiev is set to hold fresh presidential elections.
Vladimir Konstantinov, speaker of Crimea's parliament, said on Thursday the autonomous republic appointed a new prime minister, Sergei Aksenov, with Yanukovich's approval.
Ukraine's interim government has issued an arrest warrant for Yanukovich, accusing him of being responsible for the deaths of at least 70 protesters on February 21 protests in Kiev.