Hundreds of Saudi Shi’ites in the oil-producing east took to the streets in protest on Thursday, calling for the release of prisoners held without trial and an end to human rights violations, activists said.

The main rally took place in the Shi’ite centre of Qatif in the Eastern Province and a smaller one in a nearby village. Activists said there was very little police presence.

“Now in the centre of Qatif there are around 500 men and women, carrying candles and chanting for the release of prisoners and their right to protest,” said one activist who declined to be named for fear of being detained.

Another activist said around 50 women gathered in Awwamiya village, near Qatif, also carrying candles and chanting for the release of prisoners held without trial and for an end to female discrimination in the absolute monarchy.

A police spokesperson in the Eastern Province did not answer calls for comment.

Saudi Arabia, the world’s top oil producer and major U.S. ally is an absolute monarchy that does not tolerate any form of dissent. It has not seen the kind of mass uprisings that have rocked the Arab world in the last few months.

Shi’ites in the Eastern Province have held some protests over the past few weeks, resulting in police detentions of some of the demonstrators, but almost no Saudis answered a Facebook call for protest on March 11, amid a huge security presence.

Saudi Arabia’s Shi’ite minority, mostly living in the Eastern Province which holds much of the country’s oil wealth, have long complained of discrimination, a claim the government denies.