Saudi Arabia has put 32 people on trial, including 30 members of its own Shi'ite Muslim minority, on charges of spying for Iran.
The 32 defendants, including an Iranian and an Afghan, were detained in 2013 in a series of arrests that sparked concerns among Saudi Shi'a who said several are well-known figures in their community who are not involved in politics.
The charges include establishing a spy ring with members of Iranian intelligence and passing them sensitive military information, seeking to sabotage Saudi economic interests, undermining community cohesion, and inciting sectarian strife.
The trial could stoke tensions between local Shi'ite and Sunni Muslims and with Iran.
In January, Riyadh broke off diplomatic ties with Iran after the Saudi Embassy in Tehran was stormed by protesters angered about the execution of a Shi'ite cleric by Saudi authorities.