Assange is currently being held at a central London police station, before being presented before Westminster Magistrates' Court "as soon as is possible".
Video shows Assange was pulled from the embassy by half a dozen people. He could be heard yelling "The UK has no civility" and "resist this offence by the Trump administration".
Moreno specifically cited Assange's involvement in WikiLeaks as the meddling in the internal affairs of other countries, referring to the leaking of documents from the Vatican in January.
WikiLeaks has characterized Assange's expulsion as retribution for its reporting on corruption accusations against Moreno.
"If President Moreno wants to illegally terminate a refugee publisher's asylum to cover up an offshore corruption scandal, history will not be kind," WikiLeaks said in a statement.
Assange has been living in the embassy for almost seven years. A warrant was issued for his arrest on June 29, 2012 after he failed to surrender to Westminster Court.
A spokesman for the Ecuadorian Embassy confirmed Assange had been kicked out for "violating international conventions".
Assange sought asylum at the embassy after he released thousands of secret documents through WikiLeaks, some of which humiliated the US government.
Criminal charges were filed against Assange by the US Justice Department back in 2012 related to the publication of the classified documents.
The 47-year-old also faces one charge in Britain for failing to show up for court.
In a statement, the Minister of State for Europe and the Americas, Sir Alan Duncan, said the UK was grateful to Ecuador.
"It is absolutely right that Assange will face justice in the proper way in the UK. It is for the courts to decide what happens next," Sir Duncan said.
"We are very grateful to the government of Ecuador under President Moreno for the action they have taken.
"Today's events follow extensive dialogue between our two countries. I look forward to a strong bilateral relationship between the UK and Ecuador in the years ahead."
A warrant was also issued for Assange's arrest in Sweden, related to sexual assault charges.
Nearly 7yrs after entering the Ecuadorean Embassy, I can confirm Julian Assange is now in police custody and rightly facing justice in the UK. I would like to thank Ecuador for its cooperation & @metpoliceuk for its professionalism. No one is above the law
Assange strongly denied the charges and Sweden has since withdrawn its arrest warrant.
The sexual assault charges, that could've seen the WikiLeaks founder extradited to Sweden, were why Assange originally sought asylum in the embassy in June 2012.
Ecuador gave Assange citizenship in December 2017 but he has long been an annoyance for the staff at the embassy.
A hint Assange was wearing out his welcome came in March 2018, when Ecuador cut off his Internet access, saying he'd breached an agreement not to interfere in the affairs of other states.
The embassy didn't specify what Assange had done, but the move came after he tweeted criticism of Britain's assessment that Russia was responsible for the poisoning of a Russian former double agent and his daughter in the city of Salisbury.
Ecuador imposed tighter house rules last fall. Among the demands were that Assange pay for his medical and phone bills and clean up after his cat.
Assange sued the Ecuadorian government in October, accusing the country of violating his civil rights.
Assange on US' radar since at least 2010
Ahead of the US election in 2016, WikiLeaks released tens of thousands of emails that had been stolen from the Democratic National Committee and from Hillary Clinton's campaign chairman, John Podesta, in cyber-hacks that US intelligence officials concluded were orchestrated by the Russian government.
When Special Counsel Robert Mueller indicted 12 Russian military intelligence officers, he charged that they "discussed the release of the stolen documents and the timing of those releases" with WikiLeaks - referred to in the indictment as "Organization 1" - "to heighten their impact on the 2016 presidential election."
But Assange has been on US prosecutors' radar screen since 2010, when WikiLeaks' publication of 250,000 diplomatic cables and hundreds of thousands of military documents from the Iraq War prompted denunciations by then-Secretary of State Hillary Clinton and senior Pentagon officials.
The Army private who had passed the material to WikiLeaks, Chelsea Manning, was tried, convicted and served seven years of a 35-year prison term before having her sentence commuted by President Barack Obama as he left office. She was jailed again last month for refusing to testify before a grand jury investigating Assange.
In the last administration, Attorney General Eric Holder decided against pursuing prosecution of Assange out of concern that WikiLeaks' argument that it is a journalistic organization would raise thorny First Amendment issues and set an unwelcome precedent.
The Trump administration, however, revisited the question of prosecuting members of WikiLeaks, and last November a court filing error revealed that Assange had been charged under seal.
Conspiracy, theft of government property or violating the Espionage Act are among the possible charges.
Some federal prosecutors say a case can be made that WikiLeaks is not a journalistic organization. As if to lay the groundwork for such an argument, in April 2017, then-CIA Director Mike Pompeo, now secretary of state, characterized WikiLeaks as a "nonstate hostile intelligence service" and a threat to US national security.
Pompeo also noted then that the intelligence community's report concluding Russia interfered in the 2016 election also found that Russia's primary propaganda outlet, RT, "has actively collaborated with WikiLeaks."
'We really don't care about Assange'
Assange's expulsion from Ecuador's embassy reflects a shift in the country's politics since it first extended refuge to him.
The leftist former President Rafael Correa, now living in Belgium, is wanted for arrest in his homeland over alleged links to a 2012 political kidnapping. Correa was viewed as a member of an anti-Washington gaggle of South American leaders, including Venezuela's Nicolás Maduro and Bolivia's Evo Morales. He kicked out the US ambassador in 2011.
The more moderate Moreno, in sharp contrast, has sought to mend frayed ties with the United States, Ecuador's largest trading partner, and has dismissed Assange as "a stone in my shoe."
In June 2018, Vice President Mike Pence visited Quito, the capital, as part of the most senior US delegation sent to Ecuador in years.
"Our nations had experienced 10 difficult years where our people always felt close but our governments drifted apart," Pence said. "But over the past year, Mr. President, thanks to your leadership and the actions that you've taken have brought us closer together once again. And you have the appreciation of President Trump and the American people."
Sebastián Hurtado is president of Prófitas, a political consulting firm in Quito.
"I think the president has never been comfortable with Assange in the embassy," he said.
"And it's not like this is an important issue for most Ecuadorans. To be honest, we really don't care about Assange."
The Moreno administration had made no secret of its desire to unload the issue. In December 2017, it granted Ecuadoran citizenship to Australian-born Assange and then petitioned Britain to allow him diplomatic immunity. The British government refused, saying the way to resolve the stalemate was for Assange to "face justice."
- With News.com.au, Daily Telegraph, Washington Post