Saudi Arabia has arrested 10 more suspects in what it says is a spy ring linked to Iran, state media report.
Those detained include eight Saudis, a Turk, and a Lebanese citizen. Eighteen people were arrested in the same case in March.
Saudi Arabia, which is predominantly Sunni Muslim, has recently repeatedly found itself at odds with Iran, an overwhelmingly Shia Muslim nation.
Iran has denied any involvement in spying in Saudi Arabia.
Those arrested in March included an Iranian, a Lebanese and 16 Saudis. The Lebanese suspect has subsequently been released, officials said.
Shortly after their detention, the Saudi authorities said the suspects were gathering information about installations and vital areas, and were linked to Iranian intelligence services.
Saudi Arabia's Shia minority is concentrated in the country's eastern province, and community leaders there were quoted by Reuters news agency as saying all the Saudi suspects detained in March were Shia.
Tensions between Riyadh and Tehran deepened in 2011 when Saudi Arabia deployed troops to the Gulf island kingdom of Bahrain to help crush an uprising there.