An investigator for the UN Human Rights Council urged member states on Thursday to pressure Saudi Arabia to free women activists before a G20 nations summit which Riyadh will be hosting in November.At least a dozen prominent women's rights activists were arrested in Saudi Arabia in 2018 as it lifted a ban on women driving cars, a step that many of the detainees had long campaigned for. The women were rounded up as part of a broader crackdown on dissent that extended to clerics and intellectuals.In a speech to the council in Geneva, Agnes Callamard, the UN special rapporteur on extrajudicial, summary or arbitrary executions, said Saudi Arabia should release "prisoners of conscience, women, human rights defenders that are currently in prison for demanding the right to drive".There was no immediate comment from Saudi Arabia, the current chair of the Group of 20 major economies.Several of the arrested women have alleged torture and sexual assault in detention. Saudi officials deny this and said the detainees were suspected of having harmed Saudi interests and offered support to hostile elements abroad.Some of the activists are now on trial, but few charges have been made public. Charges against at least some of the activists relate to contacts with foreign journalists, diplomats and human rights groups.Their prosecution has drawn global criticism, particularly following the 2018 murder of journalist Jamal Khashoggi by Saudi agents inside the kingdom's Istanbul consulate.The families of some of the activists, included Loujain al-Hathloul, raised concerns earlier this year when they were unable to contact their detained relatives in prison for several weeks. Contact was eventually restored.Callamard, who led a U.N. investigation into Khashoggi's killing, also said that "far more needs to be done" internationally regarding accountability for his death.She welcomed efforts by Turkey, which last week began trying 20 suspects in absentia over Khashoggi's killing. Callamard attended those proceedings.