Ecuador has said it has found a hidden microphone inside its London embassy where WikiLeaks founder Julian Assange is living.
Its foreign minister Ricardo Patino said it will disclose who controls the device later.
He said the microphone was found inside Ambassador Ana Alban's office at the time of a visit to the embassy by Mr Patino to meet with Mr Assange on 16 June.
Mr Assange lives and works in a different room within the embassy.
He has been there for over a year to avoid extradition to Sweden to face rape allegations, which he denies.
The British Foreign Office declined to comment immediately on the allegation and Prime Minister David Cameron's spokesman said he did not comment on security issues.
Mr Assange fears that if he is sent to Sweden he could be extradited from there to the United States to face potential charges over the release of thousands of confidential US documents on WikiLeaks.
"We regret to inform you that in our embassy in London we have found a hidden microphone," Mr Patino told a news conference in Quito yesterday.
"I didn't denounce this at the time because we didn't want the theme of our visit to London to be confused with this matter," he said.
Mr Patino had discussed Mr Assange with British Foreign Secretary William Hague during his visit to London last month.
"Furthermore, we first wanted to ascertain with precision what could be the origin of this interception device in the office of our ambassador," he said.
"We are sorry to say so, but this is another instance of a loss of ethics at the international level in relations between governments," he added.
Ecuador's protection of Mr Assange has strained relations with Britain.
The Foreign Office said after the meeting between Mr Hague and Mr Patino on 17 June that no substantive progress had been made to break the legal and diplomatic deadlock.
WikiLeaks used its Twitter account to condemn the hidden microphone.
"Sieging/bugging of Ecuador's London embassy and the blockading of Morales jet shows that imperial arrogance is the gift that keeps on giving," the anti-secrecy group said