The United Nations human rights chief has voiced alarm at the excessive use of force by authorities in Bahrain, including the killing of two peaceful protesters, and urged respect for the right to demonstrate.

Ali Abdulhadi al-Mushaima, 27, was shot on Monday and Fadhel Salman Matrook, 32, was killed on Tuesday by members of Bahrain's security forces, according to a news release issued yesterday by the Office of the High Commissioner for Human Rights (OHCHR).

"I urge the authorities to immediately cease the use of disproportionate force against peaceful protestors and to release all peaceful demonstrators who have been arrested," said High Commissioner Navi Pillay.

"Too many peaceful protestors have recently been killed across the Middle East and North Africa," she added.

"Authorities everywhere must scrupulously avoid excessive use of force, which is strictly forbidden in international law. They must conduct prompt, impartial and transparent investigations where there have been breaches of this obligation."

Protests calling for democratic change have erupted in recent days in Bahrain, Yemen and Libya following popular uprisings in Tunisia and Egypt that led to the ouster of long-time rulers there.

Pillay stressed that lasting social stability could only be built on the foundations of the freedoms of expression and of peaceful assembly, adding that Bahrain, as a State party to the International Covenant on Civil and Political Rights, must fully respect its human rights obligations.

OHCHR had been working on establishing a dialogue with the authorities since the political crackdown that began in the country in August 2010.

"I have been urging the authorities to curb the excesses of the security apparatus and to undertake serious investigations into allegations of torture and abuse of detention rights of hundreds of political and human rights activists," said the High Commissioner.