DUBAI (Reuters) - Bahrain’s public prosecutor has appealed a court ruling that acquitted three senior leaders of the country’s main opposition group on charges of spying for Qatar, state news agency BNA reported on Wednesday.

FILE PHOTO: Bahrain's main opposition party Al Wefaq leader Sheikh Ali Salman speaks to Reuters at the party's headquarters in Bilad Al Qadeem, west of Manama, October 28, 2014. REUTERS/Hamad I Mohammed/File Photo

The ruling was a rare victory for the political opposition which has been targeted by an official crackdown since 2011 when “Arab Spring” protests rocked the kingdom, prompting a Gulf Arab bloc to send troops to put down the uprising.

In November, the prosecutor accused Sheikh Ali Salman, secretary general of al-Wefaq group, and Sheikh Hassan Sultan, a former member of parliament for al-Wefaq, of conspiring with Qatari officials to carry out “hostile acts” in the kingdom.

Last week, the High Criminal Court acquitted them along with a third senior al-Wefaq member, Ali Alaswad. The United States welcomed the verdict and called for the release of Salman, who is already serving a four-year sentence for other charges.

Bahrain, where a Sunni Muslim royal family rules over a Shi’ite-majority population, has had a febrile political environment in recent years. Demonstrators have clashed frequently with security forces, which have been targeted by several bomb attacks.

Along with Saudi Arabia, the United Arab Emirates and Egypt, Bahrain cut diplomatic and trade ties with Qatar last year, accusing it of supporting terrorism and cosying up to Iran. Doha denies the charges.

Bahrain has also frequently accused regional Shi’ite power Iran of fomenting unrest. Manama says Qatar has supported protests and the sporadic attacks against security forces, which Doha likewise denies.

BNA quoted a statement from the prosecutor’s office saying that the court ruling had many legal flaws.

“The case had much evidence that cannot be denied or rejected, leaving no doubt that the defendants had committed hostile acts against the kingdom in order harm its national interests,” it said.

The statement did not name Qatar, but it said Salman admitted to talking to an official of “that country”. The appeal hearing has been set for Sept. 5, it added.

Alaswad, who has lived in London since 2011, told Reuters last week that the public prosecutor had used secret witnesses and a video from a Bahraini television channel which experts described as edited and incomplete.

Both Bahrain and Qatar are close U.S. allies: Bahrain hosts the main U.S. naval base in the Gulf, while Qatar hosts the main U.S. air base.