GENEVA  — Thirty-two countries, including the United States and Britain, expressed concern on Monday about Bahrain’s human rights record, urging the Western-allied kingdom to protect the right to peaceful assembly and address reports of torture.

The letter, read out by Switzerland to the U.N. Human Rights Council, welcomed “positive steps” by Bahrain to improve observance of human rights, including the creation of a unit to investigate abuses by security forces.

“However, the human rights situation in Bahrain remains an issue of serious concern to us,” said the letter, read by Swiss Ambassador Alexandre Fasel.

“We are concerned about reports of harassment and imprisonment of persons exercising their rights to freedom of opinion and expression and of peaceful assembly and association, including human rights defenders,” it said.

The letter said there were not enough guarantees to a fair trial and criticized the detention of minors who took part in demonstrations. “We are concerned there is insufficient accountability for human rights violations,” it said.

Bahrain, home to the U.S. Navy’s Fifth Fleet, was swept by unrest during the 2011 “Arab Spring” uprisings when protests demanded political reforms.

Since then there have been sporadic protests and a growing number of bomb attacks that the government attributes to dissidents with links to  Iran. Iran denies any role in subversion or violence in Bahrain.

The opposition says the government is attempting to stifle free speech by jailing peaceful political dissidents.

The letter called upon the government “to appropriately address all reports of torture and ill-treatment of detainees and ensure full investigation and prosecution of these cases.”