The police said they were invited into the embassy by Ecuador's ambassador after the Ecuadorian government withdrew Assange's asylum.
Ecuador's president Lenin Moreno said a tweet that his government withdrew Assange's status for repeated violations of worldwide conventions.
He could now face an extradition request from the US over WikiLeaks' involvement in releasing sensitive military documents from US Army whistleblower Chelsea Manning in 2010 and leaking Democratic National Committee emails during the 2016 presidential elections.
That probe was later dropped, but Assange fears he could be extradited to face charges in the U.S., where prosecutors are investigating mass disclosures of classified information through WikiLeaks.
The 47-year-old Australian, who denies the rape claims, said he feared Sweden would pass him on to U.S. authorities if he was extradited.
The Wikileaks Twitter account posted: "Ecuador has illigally [sic] terminated Assange political asylum in violation of worldwide law".
WikiLeaks believes that the United States is working with Ecuador to extradite Assange to face charges, and that the embassy documents were "quite likely shared with the Trump administration", although it offered no proof of this.
However, Ecuadorian President Lenin Moreno said that Assange had violated the terms of his asylum after material regarding a corruption investigation into Moreno was published on Wikileaks.
In a tweet, it said Ecuador already had an agreement with the United Kingdom for Assange's arrest. Video show a bearded Assange being dragged out of the embassy and placed in a waiting police van. He also faced arrest in Britain for jumping bail.
Russian President Vladimir Putin's spokesman says Russia wants Julian Assange's rights to be observed following his arrest.
"He has hidden from the truth for years and years and it is right that his future should be decided in the British judicial system", Hunt said.
The first warning that Assange would be evicted from the embassy came in the form of a thread of tweets from the official WikiLeaks account a week prior.
Julian Assange, the founder of WikiLeaks, was taken into custody Thursday, seven years after he was wanted by European authorities.