By Asma Alsharif
JEDDAH (Reuters) - Security forces were blockading roads around a desert prison in central Saudi Arabia on Monday where relatives of inmates were staging a demonstration to demand their release - a rare protest in the world's biggest oil exporter.
More than 100 people, including 13 children, had gathered since Sunday afternoon in the desert around the prison in Qassim province but were told by police they would be arrested if they tried to leave, protesters said by telephone.
The complained they had no food or water because of the bloackade but said they would keep up the protest.
"We will stay here and not move until they listen to our demands and that is the release of our jailed relatives," said protester Reema al-Juraish, who said her husband, a nurse, has been held for eight years without charge.
Some of the inmates were in jail on security-related charges or for political activity but others had not been charged.
A spokesman for Saudi Arabia's Interior Ministry did not respond to calls or messages late on Sunday or on Monday requesting comment.
Protests are banned in Saudi Arabia, a monarchy with almost no elected bodies, but relatives of people held on security charges, sometimes for long periods without trial, have demonstrated several times since the start of last year.
Tarfiya prison is in the desert, 15 kms (10 miles) from the nearest village. Police on Sunday set up checkpoints on the two roads leading to it and patrol the desert around it to prevent people from entering or leaving, protesters said.
"We are hungry and thirsty and looking for shade under vehicles," one protestor who declined to be named for fear of being arrested told Reuters by telephone.
A crying baby could be heard in the background.
Four buses had arrived on Monday carrying security forces personnel with shields and batons.
Saudi Arabia avoided the kind of civil unrest that toppled leaders across the Arab world last year after it introduced generous social spending packages and issued a religious edict banning public demonstrations.
King Abdullah has pushed through some economic and social reforms in his seven-year reign, including cautious moves to improve the position of women and religious minorities, but he has left the political system untouched.
The world's top oil exporter is an important ally of Western countries in battling al Qaeda, which carried out a campaign of attacks in the kingdom from 2003-06.
Last year the Interior Ministry said it had put on trial 5,080 of nearly 5,700 people it had detained on security grounds.
In April, a court in Riyadh sentenced Mohammed al-Bajadi, a prominent rights campaigner, to four years in prison. He had been held for a year without charges after voicing support for families of prisoners demonstrating for the release of jailed relatives.
In a separate gathering on Monday, dozens of protesters rallied in front of the government-linked Saudi Human Rights Commission also calling for the release of jailed relatives.
"We are calling for human rights which they have been deprived of," said one protester who declined to be named for fear of being arrested
"There are some prisoners who have been tortured, some who have completed their sentences, others who have not been charged and even some who have been found innocent but are still imprisoned. We will stay here until we are heard," he said.
(Writing by Asma Alsharif; Editing by Angus McDowall and Angus MacSwan)