DUBAI — An international rights group urged Saudi Arabia on Sunday to stop prosecuting and punishing people for peaceful protests, after the kingdom charged 19 men for staging a sit-down demonstration outside a prison last month.

Security forces arrested dozens of men after the Sept. 23 protest near Tarfiya prison in central Saudi Arabia to press for the release of detained relatives. Demonstrators and a rights activist said police had kept the protesters, including women and children, without food or water for nearly a day.

In a separate demonstration on the same day, dozens of protesters gathered in front of the government-linked Saudi Human Rights Commission also calling for the release of jailed relatives.

Human Rights Watch said the Saudi Bureau of Investigation and Prosecution charged the 19 men on Oct. 17 with "instigating chaos and sedition" and "gathering illegally."

The following day, 15 of them were sentenced to between three and 15 days in jail. The court also handed the men suspended sentences of between 50 and 90 lashes and suspended jail terms of between two and five months.

The rest are scheduled to be tried on Nov. 4.

"Instead of addressing the protesters' concerns, the Saudi government has used the judicial system to punish them," said Joe Stork, deputy Middle East director at Human Rights Watch.

"The sentences handed to these men are part of a wider effort to target and harass activists across the country."

Saudi officials were not available to comment on the report.

Saudi Arabia, a key Gulf ally of the United States and the world's top oil exporter, banned protests in March 2011, after demonstrations began sweeping the Arab world in what became known as the Arab Spring.

In a statement on Oct. 12, the Interior Ministry warned Saudis to "refrain from staging rallies or taking part in any gathering or procession in violation of the law" and that those detained for doing so would be dealt with harshly.

Human Rights Watch said that Saudi authorities had not accused the protesters of violence during the sit-down protest.

Saudi Arabia, which has been a target for al-Qaida attacks, say the protesters' relatives were all being held on security grounds. But activists say some are also held for purely political activity and have never been charged.

An Interior Ministry spokesman said those accused of "terrorism-related" crimes were being dealt with in a fair judicial process.

Human Rights Watch said Saudi authorities had cracked down on activists for organising peaceful demonstrations in various parts of the country, including the capital Riyadh.

In April, a court in Riyadh sentenced campaigner Mohammed al-Bajadi to four years in prison after he was accused of forming a human rights association, tarnishing Saudi Arabia's reputation, questioning the independence of the judiciary, and owning illegal books, activists said.

He had been held for a year without charge after voicing support for prisoners' families.