KHARTOUM, Sudan — President Omar Hassan al-Bashir of Sudan, the country’s longtime leader, was declared re-elected on Monday, winning 94 percent of the vote in balloting that was boycotted by opposition groups and marred by low turnout and public apathy.

Mukhtar al-Asam, head of the Sudanese Elections Committee, said that 46 percent of eligible voters across the country had cast presidential ballots in four days of voting that began April 13, and that the turnout was lowest in the capital, Khartoum, and its surroundings, at just 34 percent.

“The elections were useless,” said Mouyaser Hasan, 26, an engineer in Khartoum who said he did not vote.

Fifteen largely unknown candidates ran for the presidency against Mr. Bashir, Sudan’s leader for the last 25 years, and the only sitting head of state under indictment for genocide and war crimes by the International Criminal Court.