The US Justice Department said Assange was being charged with a computer hacking conspiracy relating to his work with former US intelligence analyst Chelsea Manning in March 2010.
Ecuador granted citizenship to Assange in 2018, Reuters reported, as part of an effort to give Assange a pathway out of the embassy.
Assange hadn't left the embassy since August 2012, fearing that if he stepped off Ecuador's diplomatic soil he would be arrested and extradited to the USA for publishing thousands of classified military and diplomatic cables through WikiLeaks.
The conviction comes after Ecuador President Lenin Moreno abruptly withdrew the country's offer of asylum in its London embassy to Assange on Thursday.
He was facing extradition to Sweden on sexual assault allegations he vehemently denies, which have since been dropped.
Australian-born Assange was arrested by United Kingdom police on Thursday morning at the Ecuadorean embassy where he had been holed up for almost seven years.
Assange's lawyer, Jennifer Robinson, tweeted that her client "has been arrested not just for breach of bail conditions but also in relation to a USA extradition request". One was the release of the "collateral murder" video that showed a USA helicopter crew callously gunning down Iraqi civilians in 2007, further exposing the murderous nature of the US occupation of that country.
"Today I announced that the discourteous and aggressive behavior of Mr". However, Ecuador revoked his asylum and the country's ambassador invited London police inside the embassy to take Assagne into custody.
He listed a series of alleged transgressions by Assange during his time at the embassy, including installing electronic equipment that was not allowed, blocking security cameras, mistreating guards, and accessing embassy security files without permission.
Barely 24 hours into an official election campaign, Morrison said Assange would receive the same support as any other Australian in trouble overseas, and the extradition is a "matter for the United States".
Prime Minister Theresa May welcomed the arrest, confirming that Assange was "also arrested in relation to an extradition request from the USA authorities".