Rights groups have called on US President Barack Obama to help free human rights activists imprisoned by the Arab monarchies of the Persian Gulf countries.

In an open letter published Saturday by the [Persian] Gulf Center for Human Rights ([P]GCHR), eleven non-governmental organizations, including Reporters Without Borders and Human Rights First and Front Line Defenders, urged Obama “to press for the release of all detained human rights defenders across the [Persian] Gulf region who are imprisoned solely due to their peaceful and legitimate human rights work.”

The letter comes as Obama is to attend a [Persian] Gulf Cooperation Council ([P]GCC) summit in Riyadh, Saudi Arabia, on April 21, which is to focus on the fight against terrorist groups and regional conflicts, according to the White House.

The [P]GCC includes Saudi Arabia, Kuwait, Oman, Bahrain, Qatar and the United Arab Emirates.

“Instead of working with human rights defenders to combat extremism and build tolerant societies, authorities in the [P]GCC countries have jailed dozens of them, in some cases for life, simply for exercising their right and duty to promote and protect human rights via freedoms of expression, association and peaceful assembly,” the letter said.

The signatories reminded Obama of his “promises made in 2011 to support popular movements for reform across the region”.

The letter comes as rights groups have criticized Saudi Arabia for human rights violations and handing down long-term sentences to anti-regime protesters.

Last month, Amnesty International called on the United Nations Human Rights Council (UNHRC) to hold Saudi Arabia accountable for its “gross human rights violations.”

“Since becoming a council member in 2014, Saudi Arabia has carried out gross and systematic violations of human rights causing significant deterioration of its human rights situation. It has also breached international humanitarian law in the conflict in Yemen,” the London-based rights group said in a statement delivered during the 31st meeting of the council on March 15.

The Arab kingdom has also enforced an “abusive” anti-terror law, which equates peaceful protests with terrorism and allows it to hand down lengthy jail terms to peaceful critics and human rights activists after holding “deeply unfair” trials for them, the statement added.

Human rights advocates have also repeatedly called for an end to the oppressive treatment of dissent in Bahrain.

The Manama regime has been using fatal heavy-handed measures to crack down on peaceful protesters since February 2011. Hundreds of protesters and rights activists, including major opposition figures, remain behind bars in Bahrain’s notorious prisons.