Julian Assange was arrested inside the Ecuadorian embassy in London after British police were invited into the building by the ambassador following his government's withdrawal of asylum.
The WikiLeaks founder had been holed up for nearly seven years to avoid extradition, initially to face allegations of sexual assault in Sweden and then to the US over the leaking of classified documents.
Ecuador's President Lenin Moreno issued a statement on Twitter in which he said Ecuador had decided to terminate the diplomatic asylum granted to Assange after he had "violated, repeatedly, clear cut provisions of the conventions on diplomatic asylum of Havana and Caracas, despite the fact that he was requested on several occasions to respect and abide by these rules".
Moreno said Assange had shown "discourteous and aggressive behaviour" against Ecuador, which has hosted the WikiLeaks founder in its London embassy for six years and 10 months.
He went on to say that Assange had "particularly violated the norm of not intervening in the internal affairs of other states", referencing WikiLeaks' publication of Vatican documents in January 2019 as a recent example.
"The patience of Ecuador has reached its limit on the behaviour of Mr Assange," said Moreno, accusing Assange of installing electronic and distortion equipment, blocking security cameras, confronting and mistreating guards, and accessing embassy security files without permission.
Ecuador's Foreign Minister Juan Valencia said Assange's citizenship will be "suspended".
Moreno inherited the situation following his election in 2017 and spoke of Assange's violations of the conditions of his asylum to the Ecuadorian radio broadcasters association on April 2.
Assange's asylum began during the presidency of Rafael Correa.
In November 2010, an international arrest warrant was issued for Assange for questioning about allegations of rape and molestation in Sweden.
Assange denied the claims and surrendered himself to British police. The following month he was granted conditional bail after a hearing in London but in November the following year, lost an appeal to avoid extradition to Sweden.
He first entered Ecuador's embassy in London in June 2012. He was granted asylum by Ecuador two months later and has remained at the embassy ever since, despite Sweden announcing it had dropped its rape investigation in May 2017.
During his residency, Assange claimed he could not leave the Ecuadorian embassy for fear of being extradited to the US to face questioning about WikiLeaks' involvement in the releases of classified US documents.
In his statement Moreno said he had "requested Great Britain to guarantee that Mr Assange would not be extradited to a country where he could face torture or the death penalty".
He said the British government had confirmed this in writing.