Bulgarian Prime Minister Boyko Borissov said he had a “general malaise” after testing positive for coronavirus on Sunday.
Borissov made the announcement in a Facebook post and confirmed he would be remaining at home for any treatment, as recommended by his doctors.
"After two PCR tests from today, I am positive with COVID-19," the prime minister wrote, adding that all people he had been in contact with had been submitted to health authorities.
Borissov met with Keith Krach, US undersecretary of state for economic affairs, on Friday for talks, and the US embassy in Sofia has been informed of the situation.
The prime minister was forced to self-isolate late on Friday after a deputy minister with who he had been in contact tested positive.
Borissov said he had postponed all meetings and planned public appearances for the coming days.
In a response to well-wishers on Twitter, the prime minister added that he will "strictly follow the orders of the health authorities".
The number of new infections with COVID-19 has steadily risen in Bulgaria in the last two weeks, as the country also grapples with daily anti-government protests.
So far, the Balkan nation has recorded 37,889 confirmed cases of coronavirus and 1,094 deaths.
Meanwhile, in the capital Sofia, several hundred protesters rallied for the 109th day in a row, demanding Borissov's resignation.
The prime minister has been accused of allowing corruption to fester within Bulgaria, by supporting oligarchs and businesses close to his centre-right GERB party.
Borissov has denied the accusations and has said people can have their say at the next election, scheduled for March.