A Bahraini court on Monday sentenced 19 Shias to lengthy jail terms on charges of spying for Iran and plotting to overthrow the regime, judicial sources said.

Eight people were sentenced to life in prison, nine to 15 years in prison and two to 10 years in jail for espionage and inciting public dissent, according to a statement released by the counter-terrorism prosecutor’s office.

Fifteen of those convicted were also stripped of Bahraini citizenship, the statement said.

The court found the group guilty of leaking information to Iran’s elite Revolutionary Guards and Lebanon’s Iranian-backed Hezbollah and of receiving “material support” from the two forces. They were also convicted of forming a cell to “incite the public against the government and call for regime change by force”.

The prosecutor’s office said the 19 belonged to the Al-Wafaa Islamic movement, a little-known group which Bahraini authorities say is linked to the Revolutionary Guards and Hezbollah.

Speaking on condition of anonymity, a judicial source confirmed all 19 were Shias.

Dozens of Bahrainis have been jailed and stripped of citizenship since the 2011 outbreak of protests demanding an elected government in the Sunni-ruled kingdom.

A key US ally and home to the US Fifth Fleet, Bahrain has tightened its grip on dissent since 2011, drawing harsh criticism from international rights groups for its treatment of the Shia-majority population.

In April, parliament gave approval for military courts to try civilians charged with “terrorism”, a vaguely defined legal term in the kingdom.

Bahrain accuses Shia Iran of training “terrorist cells” that aim to overthrow its government, an allegation Tehran denies.