Saudi authorities have released six Shiites detained after protests in the Eastern Province last spring, bringing to 23 those released in two days, activists said on Thursday.

All those freed come from the Shiite area of Al-Qatif.

They were arrested during demonstrations supporting mass protests, led by the Shiite majority in neighbouring Bahrain, and denouncing the intervention of Saudi troops there.

The protests shook the kingdom's Eastern Province beginning last March, with a total of 332 people arrested, although only around 30 remain in custody, according to activists.

Seventeen people were freed last Tuesday, the activists said.

Fresh protests erupted early last month when 14 people, including 11 Saudi police, were wounded during clashes between security forces and protestors in the Shiite district of Al-Awamia.

The authorities say troublemakers were at the origin of the violence and were acting "at the instigation of a foreign country," an allusion to Iran.

Saudi Arabia's estimated two million Shiites mostly live in the oil-rich Eastern Province, and complain of being marginalised in the Sunni-dominated kingdom.