Two Saudi women's rights activists, one of whom tried to defy a ban on female driving, have been freed after more than two months in jail, a campaigner has said.

"Yes, Loujain is free," said the campaigner who spoke with Loujain al-Hathloul after she left prison on Friday.

Hathloul "just said that she's released and she's happy," said the activist, the AFP news agency reported.

Maysaa al-Amoudi, detained at the same time as Hathloul, has also been let out of jail, her family confirmed, according to the activist.

"Peace be upon you, good people," Hathloul tweeted late on Thursday.

She and Amoudi had been held since December 1, after Hathloul tried to drive into the kingdom from neighbouring United Arab Emirates in defiance of the ban.

Amoudi, a UAE-based Saudi journalist, arrived at the border to support Hathloul and was also arrested.

In December, activists said a court in Eastern Province had transferred the two women to a special tribunal for "terrorism" cases.

Social media activity

At the time, campaigners did not provide full details of the allegations against the pair but said investigations appeared to focus on the women's social media activities rather than the driving.

The activist who spoke did not know whether the two women were facing charges or what conditions were placed on their release.

Hathloul has 232,000 followers on Twitter. Before her arrest she tweeted details of the 24 hours she spent waiting to cross into Saudi Arabia after border officers stopped her.

Amoudi has 136,000 followers and has also hosted a programme on YouTube discussing the driving ban.