Investigators have broken up a a cell that was planning attacks in Bahrain, where tensions persist following unrest and Shiite-led protests earlier this year, officials said Saturday.
Four members of the cell were detained in Qatar and turned over to Manama, the interior ministry said.
A fifth Bahraini was arrested inside the country, ministry spokesman General Tareq al-Hasan said, quoted by state news agency BNA.
They had allegedly confessed to planning to attack the interior ministry, the Saudi embassy and a causeway linking the two countries.
Hasan said the four arrested in Qatar had been traveling by car from Saudi Arabia. Authorities seized "documents and a computer containing information of a security nature (and) details on certain vital sites," as well as dollars and Iranian rials.
"They then confessed that they had left Bahrain illegally at the instigation of others and gone to Iran," transiting through Qatar and Syria, to form an "organisation to commit armed terrorist acts in Bahrain," he added.
Sent back to Manama on November 4, they denounced a fifth accomplice, who was subsequently arrested, and the five have been turned over to the judicial authorities.
In a sign of the unease, Iran on Saturday summoned Bahrain's envoy to Tehran to protest what it called mistreatment of Iranian football players and supporters following a 2014 World Cup qualifier in Manama on Friday.
Bahrain's foreign minister, Khaled bin Ahmad Al-Khalifa, on November 1 accused Iran of eyeing the Gulf monarchy as "the crown jewel" in a campaign to penetrate the region.
King Hamad has ordered a probe into the unrest, the results of which are to be unveiled on November 23.