Bahraini police said Sunday they had arrested 47 people on charges linked to terrorism, including plots to assassinate "public figures", as well as filing charges against another 290.
Authorities have cracked down hard on dissent since mass street protests in 2011 which demanded an elected prime minister and constitutional monarchy in the Sunni-ruled, Shiite majority kingdom.
The government accuses Shiite Tehran of training "terrorist cells" in the tiny island state, located between rival regional heavyweights Iran and Saudi Arabia.
Iran denies involvement.
In a statement released by Bahrain's police force on Sunday, the interior minister said law enforcement had arrested 49 "terrorist agents" and foiled attacks across the country, including planned killings of "officials and public figures".
Police had also transferred the cases of 290 wanted persons and suspects to the public prosecutor's office, it said.
The statement did not specify the dates of the arrests but said they were part of "one of the most important preventive operations", triggered by "attacks on police" and a fire at a Saudi Aramco oil pipeline in Bahrain last year.
A key US ally and home to the US Fifth Fleet, Bahrain has drawn harsh criticism from international rights groups over its crackdown on dissent.
Dozens of Bahrainis have been jailed and stripped of citizenship since Arab Spring-inspired protests broke out in 2011.
Bahrain's parliament and king last year granted military courts jurisdiction to try civilians charged with "terrorism" -- a vaguely defined legal term.
The kingdom has also deported citizens whose nationalities had been revoked.