While Ecuador denies plans to revoke Julian Assange's political asylum, a top United Nations human rights official has vowed to investigate fresh rumors, noting that if the WikiLeaks founder is expelled from the Ecuadorian Embassy in London, he likely would be arrested by British authorities and extradited to the United States.

U.N. Special Rapporteur on Torture Nils Melzer warned in a statement Friday that "such a response could expose him to a real risk of serious violations of his human rights, including his freedom of expression, his right to a fair trial, and the prohibition of cruel, inhuman, or degrading treatment or punishment."

Melzer, who is preparing a formal request to visit Assange in London, called on Ecuadorian authorities to refrain from kicking the journalist and publisher out of the embassy or otherwise suspending his political asylum "until such time as the full protection of his human rights can be guaranteed."

The U.N. official also claimed that, according to information he has received, Assange is "at risk of extreme vulnerability, and his health is in serious decline." Given that, Melzer said Ecuador should continue providing the asylee "with adequate living conditions and access to appropriate medical care."

Should Assange come under British jurisdiction, Melzer said, the United Kingdom should refrain from sending him anywhere "until his right to asylum under refugee law or subsidiary protection under international human rights law has been determined in a transparent and impartial proceeding granting all due process and fair trial guarantees, including the right to appeal."

Assange has lived at the embassy since 2012 to avoid extradition to Sweden—which dropped its request last year—or the United States, where he would likely be prosecuted for publishing classified information, including evidence of U.S. war crimes.

Earlier this year, Assange's legal team filed an application with the Washington, D.C.-based Inter-American Commission of Human Rights (IACHR), in an effort to block his extradition to the United States and unseal the Justice Department's secret charges against him, which were accidentally revealed to the public in November.

During Assange's stay at the embassy over the past seven years, rumors of his looming extradition have been common, especially amid reports that his relationship with the Ecuadorian government has soured. The most recent concerns come directly from WikiLeaks.

The group tweeted Thursday that a "high level source within the Ecuadorian state" claimed Assange's pending expulsion from the embassy would happen within "hours to days." The pretext for the potential move is supposedly a recent leak and subsequent scandal that Ecuadorian President Lenín Moreno blames on WikiLeaks, which dismissed Moreno's charges as "completely bogus."

Following the tweet, local police in London told The Associated Press that because there is an active arrest warrant for Assange, they would be "obliged to execute that warrant should he leave the embassy." Officers were stationed outside the facility Friday morning.

The Daily Mail, a British newspaper, reported that "the London force has rented an apartment overlooking the embassy's front door to keep the building under constant surveillance."

Protesters also gathered outside the embassy in support of Assange, with some spelling "no expulsion" on the sidewalk using LED lights.

Assange's legal team said in a statement Friday that expelling him from the embassy in London would "violate international refugee law."

The Daily Mail reported that Jaime Marchán, Ecuador's ambassador to the U.K., told a journalist in London: "There is no change in the Señor Julian Assange's situation. To say we are going to take him out the embassy is an offense to Ecuador."

Ecuadorian Foreign Minister José Valencia responded early Friday in a series of tweets in Spanish.

"Rumors of the 'imminent' departure of Assange come from months ago," Valencia said. "The government will not comment on the current unfounded rumors, which are also insulting. Ecuador makes its decisions in a sovereign way and independent of other countries."

"Diplomatic asylum is a sovereign power of a state," he added, "which has the right to grant or withdraw it unilaterally when it considers it justified."