Saudi authorities on Wednesday temporarily freed a protester on trial after having been detained last year when he arrived at the site of a planned anti-government demonstration, activists told AFP.

"Khaled al-Johani was released for 48 hours during which he will remain under surveillance," an activist said, adding that his trial would continue.

"But most probably he will not be taken again into custody" after the 48 hours are over, the source said requesting anonymity.

Johani was arrested in March 2011 in Riyadh and charged with supporting demonstrations, being present at the site of a planned protest and talking to the foreign press "in a manner that harmed the reputation of the kingdom," according to Amnesty International.

On 11 March of last year, the kingdom launched a massive security operation to deter protesters from a planned "Day of Rage" to press for democratic reform in ultra-conservative Saudi Arabia.

The rallies never took place as thousands of police and security personnel set up checkpoints and deployed in the streets of the capital.

Johani is believed to be the "only protester who was able to reach the location" of the planned demonstration and was arrested "within minutes of talking to BBC Arabic about the lack of freedoms in Saudi Arabia," according to Amnesty's 22 February statement.

Sunni-dominated Saudi Arabia has been mainly spared a wave of uprisings which have shaken the region since the end of 2010. Only it's Shiite-populated east has been the site of sporadic protests.