WikiLeaks' founder Julia Assange is reportedly sick and Ecuadorian embassy officials in London have appealed to British authorities to grant the Aussie whistleblower safe passage so he can be brought to a hospital.

Reports from Voice of Russia in Moscow have indicated that Mr Assange requires immediate medical attention, with Ecuador's Deputy Foreign Minister Albuja Martinez saying in an interview that "Mr Assange has grown noticeably thinner, and we are very concerned about his health."

The former hacker has been holed up for four months in Ecuador's embassy after he broke the condition of his bail to his impending extradition to Sweden, where he is wanted by authorities to face charges of sexual assaults.

Mr Assange has consistently denied the allegations, insisting that the rape cases were mere pretext for U.S. authorities to get a hold of him. He has been claiming that Washington is after him for publishing leaked diplomatic cables that embarrassed the U.S. government.

He won an asylum from Ecuador but could not fly out from the UK as British authorities vowed to arrest him the moment he steps out of Quito's embassy compound in London.

According to Ecuadorian Foreign Minister Ricardo Patino, he had reached out to his British counterpart, William Hague, to discuss Mr Assange's health problems, adding he is hopeful that the UK government will make an exception on this particular case.

"As a result of the government of Britain's not giving safe passage, Julian Assange's health most certainly is beginning to be jeopardised and this is very serious," Mr Patino was reported by Agence France Presse (AFP) as saying on Thursday.

"We had hoped that the British government would defend and respect human rights and international law," he added.

The development, Reuters said, confirmed earlier reports by BBC that Mr Assange was looking pale in a recent interview, although the Australian national had also indicated that he was exercising regularly and eating the right food.

His situation, however, is taking its toll on Mr Assange's health, Ecuador said as Mr Patino cautioned, "I hope that we will not have cause to regret a serious situation there."

He complained too that the British side "haven't had a response . . . to see what we do if Mr Julian Assange has an emergency."

Mr Martinez added that Quito at the moment is confronted with "a very serious situation and it can affect Assange's human rights."

"If he falls ill, we will have to choose between two alternatives: to treat Assange in the embassy or hospitalise him," the Ecuadorian diplomat was quoted by Reuters as saying.

A statement issued by Britain's Foreign Office showed that no formal notice on the matter has been sent by Ecuador though it also hinted that such request could come under serious study.

"Ecuador had not told us that Mr Assange is ill. However, were they to do so, we would consider the matter," the statement said.