Bahrain, the host of a Formula One Grand Prix this weekend, is carrying out rampant human rights abuses against opposition activists despite its promises of reform, Amnesty International said Thursday.
"Four years on from the uprising, repression is widespread and rampant abuses by the security forces continues. Bahrain's authorities must prove that the promises of reform they have made are more than empty rhetoric," said Amnesty's Middle East and north Africa deputy head Said Boumedouha.
The watchdog, in a report, said Bahrain authorities arbitrarily detain activists with excessive use of force.
The report details testimonies of detainees -- some as young as 17 -- describing being beaten, tortured and threatened.
One told Amnesty he had been struck with the claw of a hammer on several parts of the body.
Those held in pre-trial detention are also routinely tortured to extract confessions, the report said.
"As the world's eyes fall on Bahrain during the Grand Prix this weekend, few will realise that the international images the authorities have attempted to project of the country as a progressive reformist state committed to human rights masks a far more sinister truth," Boumedouha said in a statement.
Bahrain, home to the US Navy's Fifth Fleet, has been rocked by unrest since security forces crushed Shiite-led protests in 2011 demanding a constitutional monarchy and an elected prime minister.
The tiny Gulf state banned public demonstrations in 2013.
At least 89 people have been killed in clashes with security forces, while hundreds, most of them Shiite, have been arrested and put on trial, human rights groups say.
Shiite opposition leader Sheikh Ali Salman is behind bars for allegedly trying to overthrow the regime.
His arrest in December shortly after he was re-elected head of Bahrain's main opposition party Al-Wefaq has sparked near-daily protests in Shiite villages.