RIYADH (Reuters) - About 40 women staged a rare demonstration in the Saudi capital Riyadh on Saturday, demanding the release of prisoners held without a trial as part of the kingdoms efforts to fight Al-Qaeda insurgents, activists said. Women clad in black gathered in front of the Interior Ministry in central Riyadh watched by a heavy police presence, a Reuters correspondent said. God, free our prisoners, read one poster held up by a woman. Police officers at the scene declined to comment. The women demand to free people imprisoned in the campaign against terrorism. Many people have been held up for a long time without trial, or have nothing to do with al Qaeda, activist Mohammed al-Qahtani told Reuters by telephone later. Amnesty International and other human rights activists have accused Saudi Arabia of having detained thousands of reform activists in its sweep against Al-Qaeda which staged a campaign inside the kingdom from 2003-06. Riyadh denies this. It was not immediately clear if the demonstrators were related to the prisoners. The protests took place at a time when hundreds of thousands of demonstrators have rallied in the streets protesting against poverty, unemployment and authoritarian rule in Tunisia and Egypt, sending shock waves through the Arab world.