Fugitive US intelligence leaker Edward Snowden on Monday vanished in Moscow after failing to take a flight to Cuba on which he was booked, as Washington angrily accused Russia of helping him escape the clutches of US justice.
Snowden, who embarrassed US President Barack Obama with his revelations of massive surveillance programmes, failed to appear on the Aeroflot flight to Havana from where he had been expected to continue to Ecuador and claim asylum.
Russia's Interfax news agency, known for its strong security contacts, confirmed that he was not on the Havana flight and quoted an informed source as saying he was likely already out of the country.
Snowden is "healthy and safe", WikiLeaks founder Julian Assange said on Monday, although he refused to reveal his whereabouts.
Snowden and the WikiLeaks staff member travelling with him, Sarah Harrison, are "healthy and safe and they are in contact with their legal team", Assange said in a teleconference, adding: "I cannot give further information as to their whereabouts."
US Secretary of State John Kerry dubbed Snowden a traitor to his country and warned both Russia and China that their relations with the US might be damaged by their refusal to extradite him.
Snowden arrived in Moscow on Sunday from Hong Kong, from where he leaked to the media details of secret cyber-espionage programmes by both US and British intelligence agencies.
He was said by Russian officials to have spent the night in a distinctly unglamourous "capsule hotel" at Moscow's Sheremetyevo airport awaiting his onward connection.
He had been expected to take Aeroflot's 1005 GMT flight Monday from Moscow to Havana after airline sources confirmed he had checked in and had a seat allocated.
He and his accompanying party Sarah Harrison, a British national working on the legal team of the anti-secrecy group Wikileaks, had been checked in on flight SU 150 to Havana, according to an AFP correspondent who saw the flight roster.
But in a dramatic sequence of events, the flight left the terminal at Moscow's Sheremetyevo airport with a pack of hopeful journalists on board and no sign of the former National Security Agency (NSA) contractor among the passengers.
Just as the plane was taking off, the Interfax news agency quoted a Russian security source and an Aeroflot source saying that he was not on board the flight to Havana.
It quoted another source familiar with the matter as saying: "Snowden, most likely, has already left the Russian Federation. He could have left on a different plane."
After the journalists learned Snowden was likely not on the plane, the doors had already been closed and there was no way out of a long 12-hour trip to Havana and back.
Adding to the mystery, he has not once been seen in public in the Moscow airport since Sunday's Aeroflot flight arrived from Hong Kong.
Russian security sources said they had no reason to arrest Snowden, who officials described as an ordinary "transit passenger" who had not crossed the border.
Meanwhile, Russia's prosecutor general Yuri Chaika met with Carlos Ramirez, president of Ecuador's court of justice in Moscow, Interfax said, without making any mention of the Snowden case.
The leaks forced Obama's administration to defend US intelligence agencies' practice of gathering huge amounts of telephone and Internet data from private users around the world.
Kerry said Monday it was "disappointing" that Snowden had been able to fly from Hong Kong to Russia, warning of consequences for ties with Moscow and Beijing.
Kerry, speaking on a visit to New Delhi, also defended the decision to seek Snowden's arrest, saying he was a traitor.
"He is an indicted individual, indicted on three felony counts," he said. "Evidently he places himself above the law having betrayed his country."
Ecuadorian Foreign Minister Ricardo Patino confirmed that the leftist Latin American country, whose embassy in London is already sheltering WikiLeaks founder Julian Assange, was considering Snowden's asylum request.
Ecuador's outspoken leftist President Rafael Correa has championed the cause of Assange and his allies, to the fury of the United States.
The US State Department has revoked Snowden's passport and asked other countries to prevent him from travelling. But a source in Russia's security agencies told Interfax that Snowden could travel without a passport.
The New York Times quoted Assange as saying his group had arranged for Snowden to travel via a "special refugee travel document" issued by Ecuador last Monday.
WikiLeaks, which had helped organise Snowden's escape from Hong Kong, blasted US "bullying" on their Twitter blog.
"US bullying Russia for Snowden's rendition is counter-productive. No self-respecting state would accept such unlawful demands," WikiLeaks said.
Snowden abandoned his high-paying job in Hawaii and went to Hong Kong on May 20 to begin issuing a series of leaks on the NSA gathering of phone call logs and Internet data, triggering concern from governments around the world.
Hong Kong, a special administrative region under Chinese rule that has maintained its own British-derived legal system, said it had informed Washington of Snowden's exit after determining that the documents provided by the US government did not fully comply with Hong Kong legal requirements.
Hong Kong leader Leung Chun-ying on Monday defended his government's decision to allow Snowden to leave the city, and said it was normal for him to discuss foreign-policy matters with Beijing.
"Under the one country, two systems, of course we surely need to communicate with the central government and discuss events that are related to foreign affairs," he said.