Ahmad Turki Al Saab, was jailed in May 2008 after seeking the removal of the governor of the southern province of Najran who he accused of discriminating against the Ismaili community, the paper said.
He was released on Sunday on the orders of the Custodian of the Two Holy Mosques King Abdullah bin Abdulaziz on the occasion of Eid Al Fitr, which ended the holy fasting month of Ramadan, Al Watan said quoting family members.
Saab was detained last year after the authorities summoned him to Riyadh to answer questions over a petition calling for the sacking of Najran governor Prince Mishal Al Saud.
Saab was kept in detention even after King Abdullah removed the unpopular governor in November and installed his own son, Prince Mishal bin Abdullah, in the position.
His release was secured on the recommendation of the current governor and came in the wake of the freeing of 17 imprisoned Ismaili activists late last month.
Saudi Shias — including Ismailis — constitute 10 to 15 percent of the 25.3 million mainly Sunni population of Saudi Arabia.
They complain that the authorities restricts their worship activities and that Shia activists are frequently jailed without charge.
In 2002, Saab was jailed after giving an interview to the Wall Street Journal alleging official mistreatment of the Ismailis.
In recent years, King Abdullah has made efforts to calm the divide, meeting with Saudi Shia leaders and calling for more religious openness.
But a Human Rights Watch report released on September 3 said that tensions between Sunnis and Shias have increased since 2006, partly due to concerns in Riyadh that Shia-majority Iran was seeking to expand its influence in the region.
