Bahrain admitted on Monday "excessive force" was used on pro-democracy protesters earlier this year as tension escalates two days ahead of the unveiling of a probe into the deadly crackdown.
Bahrain's Independent Commission of Inquiry, commissioned by King Hamad, will on Wednesday unveil the results of its investigation into alleged government misconduct during the February-March crackdown on Shiite-led protests.
As the Gulf kingdom braced for the findings of the probe, tension has escalated in Shiite areas of the Sunni-ruled nation and the opposition has vowed not to back down from demands for democratic reform.
"Regrettably, there have been instances of excessive force and mistreatment of detainees" during the deadly crackdown against protests, the Bahraini government statement said.
Authorities say 24 people, including four policemen, were killed in the unrest, while the Shiite-led opposition puts the death toll at 30. Hundreds more were injured.
The statement said authorities have begun prosecuting 20 officers involved in the crackdown, adding that more steps will be taken.
"We cannot condone mistreatment and abuses by our officials. There will be no impunity. All those responsible for abuses will be held accountable," it added.
Amnesty International urged the authorities to act on the probe's findings.
"The publication of this report gives Bahrain’s authorities a key opportunity to demonstrate that they intend to deliver justice to victims of abuse and carry through on promises of reform," it said.
Apart from trying those responsible for rights violations, "the authorities must provide reparations to the victims, reinstate those who were dismissed from work and reform legislation that criminalises public gatherings."
Anti-government protests in mainly Shiite areas outside Manama have intensified this month, resulting in clashes with security forces that have left a 16-year-old boy dead and dozens of people injured.
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On Sunday, King Hamad warned Bahrainis to steer clear of "anything that adversely affects" their unity.
The mass demonstrations which rocked Bahrain earlier this year were violently crushed as government forces used live ammunition and heavy-handed tactics in clashes with protesters.
The final blow to the protests, inspired by the Arab Spring, came in mid-March when the security forces, boosted by troops from Gulf nations, drove demonstrators out of Manama's Pearl Square -- the focal point of protests.
International rights organisations have repeatedly accused the government of violating citizens' rights, citing allegations of torture, unfair trials, excessive use of force and violent repression.
Since the protests broke out, hundreds of Shiites have been arrested, including prominent members of the opposition, medics, teachers and youth activists.
Bahrain's opposition groups at a joint news conference late on Sunday reaffirmed their commitment to democratic change.
"After the report is released, we will meet to plan our next steps," said prominent Shiite cleric Sheikh Ali Salman, who heads the powerful Al-Wefaq opposition group.
"Our demands are clear: an elected government, a parliament with full authorities, an independent judiciary, security for all and a just electoral system," he said.
"The opposition will continue with its demonstrations and protests and the peaceful actions inside and outside Bahrain, and we will not back down," he vowed.
The commission, which has interviewed thousands of opposition officials and government representatives, is composed of five lawyers and headed by international law and human rights expert Cherif Bassiouni.
In August, it was forced to close its office in Manama after it was stormed by a mob angered by media claims that the panel had cleared the authorities of crimes.
The incident demonstrated the sensitivity of the report and the potential for a new escalation if the findings released on Wednesday do not live up to the expectations of the opposition.