MALÉ, Maldives — The Maldives’ Elections Commission on Monday declared a resounding presidential election victory for the opposition candidate, and after hours of tense waiting, the country’s authoritarian incumbent conceded defeat.

The opposition candidate, Ibrahim Mohamed Solih, won more than 58 percent of the ballots cast in an election that saw almost a 90 percent turnout among eligible voters, according to the Elections Commission’s Twitter account.

But in a country with a brief but painful history of derailed democracy, the silence by President Abdulla Yameen, stretching for hours after Sunday night, had left many worried. The Supreme Court annulled a previous presidential election, and Mr. Yameen has put pressure on the judiciary to jail opponents in the past.

Mr. Yameen finally conceded defeat Monday afternoon at a news conference. “Yesterday, the Maldivian people decided what they want,” Mr. Yameen said. “I have accepted the results since yesterday. Earlier today, I met with Ibrahim Mohamed Solih, whom the Maldivian people have chosen to be their next president, and I congratulated him.”