Hatoon al-Fassi one of the four women released by Saudi Arabia

Saudi Arabia on Thursday released at least four more detained women activists pending trial, campaigners said, bringing the total number of women provisionally freed to seven.

They are among 11 activists, some of whom have accused interrogators of sexual abuse and torture during nearly a year in custody, who are standing trial over charges that include contact with foreign media, diplomats and human rights groups.

"Hatoon al-Fassi, Amal al-Harbi, Maysaa al-Manea, and Abeer Namankani were temporarily released," London-based rights group ALQST said on Twitter.

A Saudi lawyer with access to the trial in Riyadh's criminal court separately confirmed the release of the four women.

ALQST added there were unconfirmed reports about the release of a fifth woman, university student Shadan al-Anezi.

Families of at least two other women had been summoned to court at short notice, raising their hopes of bail but they were turned away without any explanation, another campaigner told news agency AFP.

There was no immediate comment from Saudi authorities.

Three other women on trial - activist Aziza al-Yousef, blogger Eman al-Nafjan and preacher Rokaya al-Mohareb - were granted temporary release in late March.

Riyadh has faced pressure from Western governments to release the women, most of whom were detained last summer in a wide-ranging crackdown against activists just before the historic lifting of a decades-long ban on female motorists.

But last month, Saudi Arabia mounted a fresh crackdown that sent shock waves through the kingdom.

Authorities arrested at least nine writers and academics, including two US citizens, in what appeared to be a targeted crackdown on supporters of the women activists on trial, campaigners said.

The son of freed activist Aziza, Salah al-Haidar, is among the two Americans detained.

It marked the first major crackdown since the brutal murder of journalist Jamal Khashoggi inside the Saudi consulate in Istanbul last October, which sparked unprecedented international scrutiny of the kingdom's human rights record.

Torture allegations

The siblings of activist Loujain al-Hathloul - one of the prominent detainees who was not among those freed on Thursday - have said they were being pressured by people close to the Saudi state to stay silent over her treatment in detention.

Hathloul was among the women who claimed to be tortured and sexually harassed in detention.

At one emotionally charged hearing during the ongoing trial, which began in March, some women broke down as they accused interrogators of subjecting them to electric shocks, flogging and groping in detention, two people with access to the trial told AFP.

Saudi prosecutors roundly rejected the accusation in court.

The detentions and trial underscore what liberal activists call increasing repression and authoritarianism under Crown Prince Mohammed bin Salman's de facto rule as he consolidates his grip on power.

"The case of the Saudi women activists underlines the dramatic changes underway in Saudi Arabia," said Kristin Diwan, of the Arab Gulf States Institute in Washington.

"The consolidation of authority has eliminated the limited space that once existed for liberal social activists."

Saudi officials have repeatedly accused the women of links to foreign intelligence agencies, while state-backed media branded them traitors and "agents of embassies".

But their charge sheets make no mention of contact with foreign spies, say campaigners who have reviewed the documents.

It was unclear when the next hearing in the high-profile trial, which Western diplomats and journalists are barred from attending, will be held.