WikiLeaks' founder Julian Assange has taken refuge in Ecuador's embassy in London and asked for asylum, officials said on Tuesday, in a last-ditch bid to avoid extradition to Sweden over sex crime accusations.

Ecuadorean Foreign Minister Ricardo Patino said his country would weigh the request from the self-styled anti-secrecy campaigner, whose website is famous for leaking hundreds of thousands of US diplomatic cables.

The appeal for protection was the latest twist in Assange's 18-month fight against being sent to Sweden, where he is wanted for questioning about allegations of rape and sexual assault made by two female former WikiLeaks volunteers.

The situation threatens to inflame tensions between the government of Rafael Correa, Ecuador's leftist and ardently anti-Washington president, and US authorities, who accuse Assange of damaging its foreign relations with his leaks.

It is also an embarrassment for Britain, whose foreign ministry on Tuesday confirmed the 40-year-old Assange was beyond the reach of its police in the Ecuadorean embassy.

'Ecuador is studying and analyzing the request,' Patino told reporters in Quito. He added that any decision would be made with 'respect for norms and principles of international law'.

The Andean nation in 2010 invited Assange to seek residency there but quickly backed away from the idea, accusing him of breaking US laws.

Since his detention, Assange has mostly been living under strict bail conditions at the country mansion of a wealthy supporter in eastern England. His associates say that amounts to 540 days under house arrest without charge. Breach of bail conditions is potentially a criminal offence.

'While the department assesses Mr Assange's application, Mr Assange will remain at the embassy, under the protection of the Ecuadorean Government,' the embassy said on its website.

'The decision to consider Mr. Assange's application for protective asylum should in no way be interpreted as the Government of Ecuador interfering in the judicial processes of either the United Kingdom or Sweden.'

Assange arrived at the embassy in London's exclusive Knightsbridge district asking for protection and complaining that his home country of Australia had abandoned him and refused to defend him, according to a statement from Ecuador's Foreign Ministry.

'Such statements (from Australia) make it impossible for me to return to my home country and puts me in a state of helplessness by being requested to be interrogated by the Kingdom of Sweden, where its top officials have openly attacked me,' the ministry quoted him as saying on its website.

According to Patino, Assange fears extradition 'to a country where espionage and treason are punished with the death penalty'. He appeared to be referring to the United States, because Sweden does not have the death penalty. Neither Sweden nor the United States has charged him with treason or spying.

Australian Prime Minister Julia Gillard, in Mexico for the G20 summit, said Australian consular officials would continue to assist Assange, adding Australia opposed any extradition of Australian citizens on charges which carry the death penalty.

'Let's be very clear about this. Australia opposes extradition in death penalty cases. We do that for every Australian citizen, we will do that for any Australian citizen,' Gillard told reporters.

'Our consular officials will be in contact with him, and also with Ecuador in London about this. But his decisions are for him to make,' Gillard said. - Reuters