Saudi Arabia has detained 10 people accused of spying for its Shi'ite Muslim regional rival Iran after arresting 18 people in the same case in March, state media reported on Tuesday.
The Sunni Muslim kingdom, the world's top oil exporter, accuses the Islamic Republic of stirring unrest among minority Saudi Shi'ites. Tehran rejects that charge and has also denied any involvement in espionage in Saudi Arabia.
"Initial investigation carried out by the authorities led to the detention of 10 others for involvement in spying activities," Saudi Press Agency quoted Interior Ministry security spokesman Major-General Mansour al-Turki as saying.
He said they included eight Saudis, a Turk and a Lebanese citizen. Those arrested in March included 16 Saudis and an Iranian. A Lebanese man also detained at that time has been released for lack of evidence, Turki said.
Local Shi'ite leaders in Saudi Arabia's Eastern Province have said the 16 detained in March are Shi'ites.
Some prominent Shi'ite clerics and other community leaders wrote to the government at the time saying they did not believe the men were spies and that the arrests might fuel tensions.
Saudi Shi'ites complain of entrenched discrimination, which the authorities deny. Nearly 20 people have been killed since early 2011 in protests and clashes between Shi'ites and security forces in Eastern Province's Qatif district.
Saudi Arabia also accuses Iran of fomenting unrest in Sunni-ruled Bahrain, where majority Shi'ites have led pro-democracy protests. Iran denies this.