RIYADH (Reuters) - Saudi Arabia has arrested 18 people, including an Iranian, a Lebanese citizen and 16 Saudis, for spying, it said on Tuesday, in a move that could raise tensions between Riyadh and arch-rival Tehran.
Interior Ministry spokesman Mansour al-Turki said on state television the suspects were "involved with a spy network working for a foreign country".
Turki later told Reuters he could not say who the 18 were suspected of spying for, pending further investigation.
Sunni Saudi Arabia and Shi'ite Iran have tussled for influence across the Middle East, including in Lebanon, and Riyadh has accused Tehran of stoking unrest in neighboring Bahrain, a charge it has denied.
The spying arrests, the first in recent memory, follow a string of accusations by Riyadh that an unnamed foreign country, widely understood to mean Iran, had instigated protests inside Saudi Arabia.
The arrests were made four days ago and the suspects were being investigated before being handed over to judicial authorities, Turki said on television.
"They were gathering information about installations and vital areas in the country and providing intelligence agencies of that state with it," he added.
Saudi Arabia has blamed persistent unrest among members of its Shi'ite minority in the Qatif district of Eastern Province, where 16 people have been killed in clashes with police over two years, on outside intervention.
In November 2011 it said a foreign power was behind an attack by protesters on a police station in Qatif. Last January it said 23 people wanted in connection with the unrest in the area were acting on behalf of another country.
In both cases the country was widely understood to be a reference to Iran, although Saudi Arabia has never explicitly acknowledged as much.
In December it said a successful attempt last August to hack the computer network of Saudi Arabian Oil Co (Saudi Aramco), had originated from servers in other countries.
Relations between Saudi Arabia and non-Arab Iran soured after the latter's 1979 revolution that brought Shi'ite clerics to power. Saudi Arabia follows the rigid Wahhabi school of Sunni Islam in which Shi'ism is seen as heretical.
Shi'ites in Eastern Province say they face persistent discrimination affecting their ability to work, study and worship freely, charges Riyadh denies.
Saudi Arabia's Interior Ministry has painted the trouble in Qatif, where there have been frequent anti-government protests since early 2011, as the work of a small number of militants. Shi'ite activists there dispute that characterization.
Unrest in Qatif flared after Saudi Arabia sent troops to Bahrain as its ruling family quashed mass protests led by majority Shi'ites. Bahrain has accused the Lebanese Shi'ite movement Hezbollah, backed by Iran, of being behind bombings there.
(Reporting by Ali Aabdelatti in Cairo and Angus McDowall in Riyadh; Writing by Sami Aboudi; Editing by Michael Roddy)