Bahrain has jailed 57 Shia citizens, and stripped all but one of them of their nationality, for an alleged plot to bomb sites across the kingdom.
The state news agency, BNA, said the group plotted to attack "policemen... vital sites and security locations, including an embassy".
Bahrain human rights groups condemned the "unfair trial" and sentences.
The Gulf state has seen sporadic unrest since putting down mass Shia-led protests in 2011.
In the latest case the defendants were given sentences ranging from three years to life in prison. Activists said minors were among those jailed. Four people were acquitted.
Among the group's targets, the Gulf Daily News reported, were the Saudi embassy in Manama and the King Fahd Causeway connecting Bahrain and Saudi Arabia.
The court alleged that those on trial were funded by the main Shia opposition group, al-Wefaq, and a banned association, al-Wafa (Fidelity).
In a statement, two Bahrain advocacy groups said that nine of those found guilty were under the age of 18.
"Bahrain's politicised courts are disenfranchising an entire generation of Bahrainis with unfair imprisonment," said Husain Abdulla, of Americans for Democracy and Human Rights in Bahrain.
Bahrain was hit by an uprising in 2011 in which the Shia majority demanded democratic reforms from the Sunni-led government. Since then, protests have been more intermittent, following a crackdown.
In January, Bahrain stripped citizenship from 72 people on the grounds of damaging national security.