Amnesty International said today that Bahrain had failed to deliver on promises of political reform after a deadly crackdown last year.

In a 58-page report released just days before the Gulf kingdom is due to host a Formula One Grand Prix, which last year was cancelled amid unrest, the watchdog said authorities "have failed to provide justice for victims of human rights violations."

"With the world's eyes on Bahrain as it prepares to host the Grand Prix, no one should be under any illusions that the country's human rights crisis is over," said Amnesty's Hassiba Hadj Sahraoui.

"The authorities are trying to portray the country as being on the road to reform, but we continue to receive reports of torture and use of unnecessary and excessive force against protests," said Ms Sahraoui, Amnesty's Middle East and North Africa deputy director, adding that so far, "reforms have only scratched the surface."

The report came just a day after a prominent international think-tank warned that Bahrain's hosting of the prestigious race was a "time bomb," amid threats of new protests against the Sunni rulers of the Shia-majority kingdom.

The International Crisis Group warned that "beneath a facade of normalisation, Bahrain is sliding towards another dangerous eruption of violence," and urged the government in Manama to heed calls for real reform.

King Hamad has promised change in line with the recommendations of an independent comission of inquiry into his government's bloody crackdown in March last year against month-long Shia-led pro-democracy protests.

The commission found that the security forces had used excessive force against unarmed protesters and tortured detainees in an operation that left 35 people dead.