The UK, meanwhile, has said it is disappointed by the decision and will not grant safe passage out of the country to Assange, who has been holed up inside Ecuador's embassy in London for nearly two months.
"Under our law, with Mr. Assange having exhausted all options of appeal, the British authorities are under a binding obligation to extradite him to Sweden. We shall carry out that obligation. The Ecuadorian government's decision this afternoon does not change that. We remain committed to a negotiated solution that allows us to carry out our obligations under the Extradition Act," said a statement from the British Foreign Office.
Patiño preceded his announcement with a lengthy argument against any British action against Ecuador's embassy in London. In remarks Wednesday, he said the Ecuadorian government had received a written notice from British authorities that they would "assault" the country's embassy in London if Ecuadorian officials failed to hand over Assange to British authorities.
"We are not a British colony," he said. "Those times are passed."
The British government's statement that it intends to honor its promise to send Assange to Sweden to face questioning on sex crimes charges, even if it means entering the premises, is an affront to international law, Patiño said.
The UK, in effect, is saying "we are going to savagely hit you depending on how you behave," the foreign minister said.
The British say one of their laws allows for it to enter the embassy and arrest Assange. Patiño cited a laundry list of international treaties and conventions that he said make it clear that it is illegal to enter another country's embassy.
Asylum was granted to Assange after considering the "maximum seriousness" of the matter, he said.
The foreign minister outlined 11 conclusions that Ecuador reached in reviewing the WikiLeaks founder's asylum request. In short, Ecuador found that Assange has a credible fear of persecution for his ideas and politics. The government described him as an activist for freedom of the press and freedom of expression who would be silenced if sent to Sweden, and possibly, the United States.
In the United States, there are no guarantees that Assange would receive a fair trial or that he wouldn't be subject to a military or secret tribunal, Patiño said.
WikiLeaks condemned Britain's vow that it would enter the embassy in a statement released early Thursday.
"A threat of this nature is a hostile and extreme act, which is not proportionate to the circumstances, and an unprecedented assault on the rights of asylum seekers worldwide," the statement said.
British police arrested at least two protesters outside the Ecuadoran embassy in London before the asylum announcement was made.
The Foreign Office said there was a larger "police presence outside the British embassy in Quito" than at the Ecuadoran mission in London.
Assange has been holed up there since petitioning for asylum in June. He is seeking to avoid being sent to Sweden over claims of rape and sexual molestation, and said he fears that if extradited, Swedish authorities could eventually hand him over to the United States.
Assange was arrested in Britain in 2010 because Swedish authorities wanted to question him about the allegations. Two women have accused him of sexually assaulting them during an August 2010 visit to Sweden in connection with a WikiLeaks release of internal U.S. military documents. Assange denies the allegations and argues they are in retribution for his organization's disclosure of American secrets.His bail conditions required he spend his nights at the home of a supporter outside London. He is subject to arrest for breaking the terms of his bail, London's Metropolitan Police said the day after he entered the embassy.
WikiLeaks has published about 250,000 U.S. diplomatic cables, causing embarrassment to the U.S. government and others. It also has published hundreds of thousands of classified U.S. documents relating to the conflicts in Iraq and Afghanistan.
Assange sought refuge at the embassy five days after the Supreme Court in Britain dismissed his bid to reopen his appeal of the decision to send him to Sweden, his last option in British courts.