Bahrain said on Saturday it uncovered a 54-member "terrorist organization" involved in prison breaks and attacks on security forces.
Police arrested 25 members of the group, 10 of whom were former inmates, German public broadcaster Deutsche Welle reported.
The remaining suspects appeared to be at large.
The suspects face 16 charges, including killing two police officers during a prison break, attempted murder of another police officer, sheltering terrorists and joining a terrorist group. Prosecutors said only four of the suspects denied the charges.
Authorities said they found "large quantities of explosives, detonators and hand grenades" alongside pistols and AK-47 assault rifles.
Bahrain's chief prosecutor Ahmed al-Hammadi was quoted as having told the state-run Bahrain News Agency that several of the group's operations had been planned from outside the country, including from Germany.
"One of the group's leaders is based in Germany, where he helped several members go to Iran and Iraq to receive training on using explosives and firearms at the Revolutionary Guard camps ahead of carrying out their terrorist crimes in Bahrain," al-Hammadi said, according to Deutsche Welle.
In February, Bahrain executed three men found guilty of perpetrating a bomb attack that led to the death of three police officers in 2014.
Bahrain regularly accuses Iran of fomenting civil unrest and supporting attacks against security forces in the country. In 2015 Bahrain recalled its ambassador from Iran over these charges, which Iran denies.
In 2013 Bahrain became the first Arab country to blacklist Iranian-backed Hezbollah as a terrorist organization.
Last year, it published a list of 68 Islamist groups it classified as "terrorist", including Al-Qaeda and its branches in Yemen and North Africa, Al-Nusra Front in Syria, and the Islamic State group (ISIS).