Bahrain's Interior Ministry said it has arrested two Gulf citizens suspected of plotting "terror" attacks against the kingdom.

The two Gulf nationals tried to enter Bahrain with forged passports through King Fahd Causeway, which joins Bahrain to Saudi Arabia, and were "carrying a large amount of money", the ministry said late on Saturday.

"The initial investigation revealed that the arrestees are former detainees of the Guantanamo detention center. They are suspected of plotting a terror act to jeopardise the security and safety of Bahrain," the ministry said in a statement.

The statement did not elaborate on the nature of the planned attacks or the identities of the two people arrested.

Bahrain has been hit by political unrest since protests led by opposition groups erupted in 2011. - Reuters