Bahrain has brutally cracked down on opponents over the past year with security forces jailing, torturing, and sexually assaulting more than 160 government critics, rights groups said on Thursday.

Between June 2016 and June 2017, at least 169 Bahrainis have also been threatened, harassed, and banned from leaving the Gulf island nation, Amnesty International said in its report, 'No one can protect you': Bahrain's year of crushing dissent.

"We have heard horrific allegations of torture in Bahrain. They must be promptly and effectively investigated and those responsible brought to justice," said Philip Luther, Amnesty's research and advocacy director for the Middle East and North Africa.

"The government of Bahrain has managed to crush a formerly thriving civil society and reduced it to a few lone voices who still dare to speak out."

One of the victims, prominent human rights defender Ebtisam al-Sayegh, said she was blindfolded, beaten, and sexually assaulted while in the custody of the National Security Agency.

"They took away my humanity," Sayegh told researchers.

An "all-out campaign" was launched to dismantle the main opposition Al-Wefaq party, Amnesty said. A prominent Shia scholar, Sheikh Isa Qassim, was stripped of his citizenship, and dozens of his followers were detained for demonstrating.

Bahrain's Ministry of Interior was asked for comment, but none was received by publication time.

Michael Payne, international advocacy officer at the Washington-based Americans for Democracy and Human Rights in Bahrain, confirmed the 169 figure cited by Amnesty. He told Al Jazeera in total there are 3,500 to 4,000 political prisoners languishing in Bahraini prisons.

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He also denounced the governments of the United States and the UK for increasing economic and military support for Bahrain, even though human rights abuses have intensified.

"This narrow focus on defence cooperation has had severe repercussions for Bahrain's human rights situation and its long-term stability and security," said Payne.

"Just days after President Trump met with Bahrain's king in Riyadh [Saudi Arabia] in May, for example, Bahraini authorities launched their deadliest raid on a peaceful protest since before 2011, killing five demonstrators and injuring hundred."

Bahrain has been in turmoil since a 2011 uprising backed by majority Shia Muslims demanding greater rights from the Sunni-led monarchy. The government crushed the protests with the help of its Sunni Arab Gulf allies suspicious of Iran and opposed to growing Shia influence in the region.