The intelligence whistleblower Edward Snowden will on Monday attempt to complete an audacious escape to the relative safety of South America after his departure from Hong Kong escalated already fraught diplomatic relations between the United States and China.

In a move that appeared to bewilder the White House, Snowden was allowed to flee Hong Kong on Sunday morning and head to Moscow on a commercial flight despite a formal request from the US to have the 30-year-old detained and extradited to face espionage charges for a series of leaks about the National Security Agency (NSA) and Britain's spy centre, GCHQ.

Arriving in Moscow, Snowden disappeared again, leaving the aircraft without being spotted, but being pursued by the Ecuadorian ambassador, Patricio ChÃ¡vez, amid speculation that he will fly to Quito on Monday, possibly via Cuba.

Snowden has asked for political asylum in Ecuador, the country that has also given shelter to the WikiLeaks founder, Julian Assange, at its embassy in London.

In a statement on Sunday night, WikiLeaks, which has been providing legal and logistical help to Snowden in recent days, said: "He is bound for the Republic of Ecuador via a safe route for the purposes of asylum, and is being escorted by diplomats and legal advisers from WikiLeaks."

"Mr Snowden requested that WikiLeaks use its legal expertise and experience to secure his safety. Once Mr Snowden arrives in Ecuador his request will be formally processed."Snowden's escape from Hong Kong infuriated US politicians, while China focused on condemning Washington over his latest disclosures, which suggested the had hacked into Chinese mobile phone companies to access millions of private text messages.

Moscow was also drawn into the controversy after it emerged that Snowden's passport had been revoked before he left Hong Kong and he did not have a visa for Russia. But Russia appeared indifferent to the uproar, with one official saying Snowden was safe from the authorities as long as he remained in the transit lounge at the city's Sheremetyevo airport.

Dmitry Peskov, spokesman for the Russian president, Vladimir Putin, said: "I know nothing."

In Washington, congressmen fulminated at the array of powers suddenly ranged against the US. Mike Rogers, chairman of the House permanent select committee on intelligence, railed at Russian president Vladimir Putin over his attitude to Snowden, suggesting an ulterior motive. "I'm sure they would love to have a little bit of coffee and some conversation with Mr Snowden," Rogers said.

The Democratic senator Chuck Schumer added: "The bottom line is very simple: allies are supposed to treat each other in decent ways, and Putin always seems almost eager to put a finger in the eye of the United States, whether it is Syria, Iran and now of course with Snowden. That's not how allies should treat each other and I think it will have serious consequences for the United States-Russia relationship."

Washington will also challenge Hong Kong over its decision to let Snowden flee. In a statement, the Hong Kong Special Autonomous Region (HKSAR) said it could not have stopped Snowden because America's request to detain him on a provisional warrant – filed in papers last week – did not fully comply with legal requirements. "As the HKSAR government has yet to have sufficient information to process the request for provisional warrant of arrest, there is no legal basis to restrict Mr Snowden from leaving Hong Kong," the statement said.

Yet the admission that Snowden had been allowed to leave was made five hours after he had boarded an Aeroflot flight to Moscow, and the discovery of the oversight came two days after the papers had been formally sent.

Snowden, a former contractor, had previously said he would stay in Hong Kong and fight for his freedom through the courts. He had been at a safe house after giving an interview to the Guardian revealing himself as the source who leaked top-secret US documents.

Since then, Snowden has been in touch with WikiLeaks, which revealed on Sunday that it had been instrumental in helping him find safe passage out of Hong Kong.

Speaking to the Sydney Morning Herald from the Ecuadorian embassy in London, Julian Assange said: "Owing to WikiLeaks' own circumstances, we have developed significant expertise in international asylum and extradition law, associated diplomacy and the practicalities in these matters. I have great personal sympathy for Ed Snowden's position. WikiLeaks absolutely supports his decision to blow the whistle on the mass surveillance of the world's population by the US government."

On Saturday, the South China Morning Post disclosed details of new documents from Snowden, which suggested the had hacked into Chinese phone companies.

For the second time in 10 days General Keith Alexander, the head of the , had to defend the agency's activities, and he did not deny the latest allegations.

"To say that we're willfully just collecting all sorts of data would give you the impression that we're just trying to canvas the whole world," Alexander said.

"The fact is what we're trying to do is get the information our nation needs, the foreign intelligence, that primary mission. The case that Snowden has brought up is in defending this nation from a terrorist attack. I'm confident that we're following the laws that our country has in doing what we do. We have a set of laws that guide how acts; we follow those laws. We have tremendous oversight by all three portions of the government: the courts, Congress and the administration."

But China's official Xinhua news agency said the revelations had "put Washington in a really awkward situation".

"They demonstrate that the United States, which has long been trying to play innocent as a victim of cyber attacks, has turned out to be the biggest villain in our age," it said.

The fall-out from Snowden's leaks continued to stir the surveillance debate in the UK, with Shami Chakrabarti, the director of Liberty, insisting David Cameron or the foreign secretary, William Hague, should address MPs.

On Friday, the Guardian revealed has put taps on some of the cables that carry internet traffic in and out of the UK, and has developed a storage system – codenamed Tempora – that can keep the information for up to 30 days.

The programme, which has not been disclosed before, allows to keep a vast amount of emails and telephone calls for analysis.

Chakrabarti said: "The authorities appear to be kidding themselves with a very generous interpretation of the law that cannot stand with article 8 of the European Convention on Human Rights.

"Revelations of blanket surveillance of the British public on such a scale amount to a huge scandal even by the standards of recent years. At the very least, the prime minister or foreign secretary should appear before the House of Commons immediately to explain how this was justified without clear legal authority or parliamentary debate."

has said it complies fully with British law.