An attorney representing three of the defendants said the country's highest appeals court took just minutes to rule on the appeal of the 13 pro-democracy activists, who received sentences of five years to life in prison, CNN reported.
The ruling was the last opportunity the activists had to reverse their convictions. They were arrested for their roles in 2011 the anti-government demonstrations known as the Arab Spring movement that swept across North Africa and the Middle East. Bahraini authorities, backed by troops from Saudi Arabia and the United Arab Emirates, cracked down on demonstrations, so they didn't gain as much momentum as those elsewhere.
The government said it provided fair trials.
Bahrain is home to the U.S. Navy's Fifth Fleet headquarters. When the convictions were upheld by a lower court in September, the U.S. State Department said it was "deeply troubled."
Amnesty International has called the convictions an outrage and urged Bahrain to overturn the sentences.
"This unjust decision will confirm the view of many that the judiciary is more concerned about toeing the government's line than upholding the rule of law and the rights of all Bahrainis," said Hassiba hadj Sahraoui, deputy director of Amnesty International's Middle East and North Africa program.
The court's decision also drew a rebuke from Great Britain, which expressed its "deep dismay" at the court's decision, The Guardian of London said. The U.K. has commissioned a parliamentary committee to examine relations with Bahrain and Saudi Arabia as a result of the crackdown.
Countering Britain's protests, Bahraini officials criticized the parliamentary committee. Officials in the two Arab countries said the committee has refused to consider evidence of improved human rights practices.
British lawmakers responded, citing procedural problems in processing the paperwork to include the countries' response in its final report.