The alleged attacks is likely to further inflame tensions in Bahrain, rocked earlier this year by demonstrations by majority Shiite Muslims demanding political reforms and equality in the Sunni-led kingdom, a U.S. ally and home of the Fifth Fleet.
On Saturday night the state news agency BNA quoted an Interior Ministry spokesman as saying that four Bahraini members of the cell were detained by authorities in neighbouring Qatar after they entered the Gulf Arab state from Saudi Arabia.
The four had documents and a computer that included details of vital installations, the news agency added.
"The Qatari security authorities questioned the suspects and enquiries in Qatar revealed that the suspects had illegally left Bahrain after being incited by others to head to Iran, passing through Qatar and Syria, to establish a group that carries out armed terrorist operations in Bahrain against vital establishments and individuals," BNA reported.
"Enquiries to date have confirmed that the suspects were targeting the King Fahd Causeway, the ministry of interior building, the Saudi Arabia embassy and individuals," it added.
The agency said the four carried unspecified sums of foreign currency, including U.S. dollars and Iranian rials, and had flights booked to Syria.
BNA said the four suspects gave information about a fifth member of the group in Bahrain, who was also arrested.
There was no immediate comment from Bahrain's opposition on the report.
Bahrain has accused Iran of being behind the unrest, which began in February with activists staging mostly peaceful protests in the capital to push for more political freedoms and better living conditions.
Bahrain asked Saudi Arabia to send forces to help it crack down on the protesters.
Bahrain has accused Shi'ite-led Iran of being behind the unrest, but Tehran denied this.
Last month, U.S. authorities said they had broken up a plot by two men linked to Iran's security agencies to assassinate Saudi Ambassador Adel al-Jubeir. One was arrested last month while the other was believed to be in Iran.