BEIRUT (Reuters) - Human rights in Bahrain have deteriorated significantly in the past year because international pressure on the Gulf Arab kingdom has weakened, activists said on Thursday.

“Bahrain is now clearly sliding in a new and very dangerous direction with 37 people arrested yesterday alone,” said Brian Dooley of U.S.-based Human Rights First.

“The fairly weak level of restraint that was there before has all but gone,” he said, adding that countries influential in Bahrain such as the United States and Britain needed to step up their criticism.

Bahrain, where the Shi’ite Muslim majority is ruled by a Sunni Muslim royal family, has pursued a crackdown on opposition activists since quashing 2011 protests calling for democracy.

Authorities have closed opposition political groupings, revoked dissidents’ passports and arrested suspected militants. Activists say many arrests are for political reasons and breach detainees’ human rights.

Bahrain, where the U.S. Navy’s Fifth Fleet is based, denies clamping down on dissent. It says it faces a militant threat backed by arch-foe Iran on the opposite side of the Gulf.

The Bahraini Embassy in Britain, responding to a request for comment, cited an earlier statement which said that the Gulf state was committed “to transparency and the protection and safeguarding of Human Rights enshrined in the Constitution, as well as in international treaties and obligations”.

Human rights activists, at a news conference in Lebanon on Thursday, said the situation has taken a turn for the worse with 19 people now sitting on death row, renewed reports of torture in detention and military courts now trying civilians.

In January 2017 Bahrain executed three Shi’ite men convicted of killing three policemen in a 2014 bomb attack. They were the first such executions in over two decades, and sparked protests.

Bahrain is due to hold parliamentary elections in 2018.

The activists also said they have concerning new information about the health of detained prominent rights campaigner Nabeel Rajab, and demand he be given access to adequate healthcare.

“Recently alarming signals have multiplied ... regarding his detention condition,” said Dimitris Christopoulos, president of human rights organization FIDH, calling for his release. Rajab is FIDH’s deputy secretary general.

Rajab, a leading figure in the 2011 pro-democracy protests, has been in and out of detention since that time. He faces up to 15 years in jail over Twitter statements he made about the war in Yemen. A verdict is expected on Feb. 21.

“Nabeel is in real danger,” said Sheikh Maytham Al-Salman from the Bahrain Center for Human Rights.

Bahraini authorities said Rajab had received medical checks twice in December and January and his health was “stable”.

“We take very seriously the safety and wellbeing, including healthcare both in terms of access and adequacy, of any person, whether in prison or in detention,” the director general of the prisons authority said in a statement.