* Russia defies calls to send Snowden to United States
* Snowden not seen on Moscow-Havana flight
* Ecuador says Snowden has requested asylum there (Adds Ecuador's foreign minister, U.S. Secretary of State)
By Lidia Kelly and Katya Golubkova
MOSCOW, June 24 Former U.S. spy agency contractor Edward Snowden's whereabouts were a mystery on Monday as Russia defied White House pressure to send him back to the United States and stop him fleeing Moscow on his globe-crossing escape from U.S. prosecution.
Snowden, whose exposure of secret U.S. government surveillance raised questions about intrusions into private lives, was allowed to leave Hong Kong on Sunday after Washington had asked the Chinese territory to arrest him on espionage charges.
The 30-year-old flew to Moscow as a transit stop before heading elsewhere, several sources said. But reports that he would fly to Cuba were put in doubt when witnesses could not see him on the plane, despite heightened security before take-off.
Ecuador, which has sheltered the founder of the WikiLeaks anti-secrecy group, Julian Assange, said it was considering Snowden's request for asylum and that human rights were it main concern. There are no direct commercial flights to Quito from Moscow.
"He didn't take the flight (to Havana)," a source at Russia's national airline Aeroflot told Reuters.
As speculation grew about where he would go next - Ecuador, Venezuela or Cuba at a later date to escape the crowd of journalists aboard Monday's flight to Havana - Washington was stung by Russian defiance.
Snowden's flight to Russia, which like China challenges U.S. dominance of global diplomacy, is an embarrassment to President Barack Obama who has tried to "reset" ties with Moscow and build a partnership with Beijing.
The White House said it expected the Russian government to send Snowden back to the United States and lodged "strong objections" to Hong Kong and China for letting him go.
U.S. Secretary of State John Kerry said during a visit to India that it would be "deeply troubling" if Moscow defied the United States over Snowden, and said the fugitive "places himself above the law, having betrayed his country".
But the Russian government ignored the appeal and President Vladimir Putin's press secretary denied any knowledge of Snowden's movements.
Asked if Snowden had spoken to the Russian authorities, Peskov said: "Overall, we have no information about him."
He declined comment on the expulsion request but other Russian officials said Moscow had no obligation to cooperate with Washington, after it passed legislation to impose visa bans and asset freezes on Russians accused of violating human rights.
"Why should the United States expect restraint and understanding from Russia?" said Alexei Pushkov, the head of the foreign affairs committee in the lower house of parliament.
Putin has missed few chances to champion public figures who challenge Western governments and to portray Washington as an overzealous global policeman. But Russian leaders have not paraded Snowden before cameras or trumpeted his arrival.
Since leaving Hong Kong, where he feared arrest and extradition, Snowden has been searching for a country that can guarantee his security.
Ecuador's foreign minister, Ricardo Patino, said during a trip to Vietnam that Quito would take into account a U.S. request about Snowden and is in "respectful" contact with Russia about him. He gave no details of the U.S. request.
"We will consider the position of the U.S. government and we will take a decision in due course in line with the (Ecuadorean) constitution, the laws, international politics and sovereignty," Patino told a news conference in Hanoi.
A source at Aeroflot said on Sunday Snowden was booked on the flight due to depart for Havana on Monday at 2:05 p.m. (1005 GMT). But a correspondent aboard could not see him and the seat he was supposed to occupy, 17A, was taken by another passenger.
It was not immediately clear whether the plane had a crew section where Snowden might have been concealed.
U.S. Senator Charles Schumer said Putin had probably known about and approved Snowden's flight to Russia, and saw "the hand of Beijing" in Hong Kong's decision to let Snowden leave.
But taking the higher ground after being accused of hacking computers abroad, the Chinese Foreign Ministry expressed "grave concern" over Snowden's allegations that the United States had hacked computers in China. It said it had taken up the issue with Washington.
Some Russians have praised Snowden's revelations. Others fear a new chill in relations with the United States.
"We are a pretty stubborn country and so is the United States. Both are mighty countries, so I would say this has a good potential to turn into a big fuss in bilateral relations," said Ina Sosna, manager of a Moscow cleaning company.
"I guess it would be best if they just let him move on from Russia to avoid any more controversy over him being here."
Snowden was assisted in his escape from Hong Kong by WikiLeaks, whose founder Assange said he had helped to arrange documents from Ecuador. WikiLeaks said diplomats and Sarah Harrison, a legal researcher working for the anti-secrecy group, accompanied him.
Ecuador, like Cuba and Venezuela, is a member of the ALBA bloc, an alliance of leftist governments in Latin America that pride themselves on their "anti-imperialist" credentials. The Quito government has been sheltering Assange at its London embassy for the past year.
Snowden, who had worked at a U.S. National Security Agency facility in Hawaii, had been hiding in Hong Kong, a former British colony that returned to China in 1997, since leaking details about secret U.S. surveillance programmes to news media.
He has been charged with theft of federal government property, unauthorised communication of national defence information and wilful communication of classified communications intelligence to an unauthorised person, with the latter two charges falling under the U.S. Espionage Act. (Additional reporting by Gabriela Baczynska and Alexei Anishchuk in Moscow, Martin Petty in Hanoi, Sui-Lee Weein in Beijing,; Andrew Cawthorne, Mario Naranjo and Daniel Wallis in Caracas, Alexandra Valencia in Quito and Mark Felsenthal, Paul Eckert and Mark Hosenball in Washington; Writing by Timothy Heritage and Elizabeth Piper, Editing by Mark Heinrich and David Stamp)