Saudi authorities have released 17 Shia activists detained in anti-government protests earlier this year, but dozens more were still in jail, activists said on Tuesday.
"Some of the released detainees have already returned to their homes while others are finalising their release papers," a human rights activist told AFP on condition of anonymity.
Another 40 Shias also taken into custody since anti-government protests in Eastern Province in spring still remain in detention, according to human rights observers.
The overwhelming majority of Saudi Arabia's estimated two million Shias live in Eastern Province, which neighbours Bahrain where authorities supported by Saudi-led Gulf troops crushed a Shia-led uprising in March.
The anti-government protests by Saudi Shias were initially triggered by the kingdom's role in the Bahrain crackdown, but they later developed into a general call for equality in the Sunni-ruled kingdom.
In early October, 14 people were wounded, including 11 Saudi policemen, when riots broke out in the Shia-majority village of Al-Awamia.
At the time, activists said the riots were triggered by the arrest of two elderly men in a bid to force their wanted sons, accused of taking part in protests, to surrender.
In total, Saudi authorities have arrested some 332 Shiites in recent months, activists estimate.