A Bahraini court convicted 57 people on Thursday of establishing a terrorist cell in the kingdom and stripped 56 of them of their citizenship, according to opposition sources.

Sixty one people were tried in the case, with the First Higher Criminal Court sentencing 52 to prison terms of between 10 and 15 years and five others receiving life sentences.

Four defendants were acquitted and released from prison.

All of those convicted were given fines of between 500 ($1,300) and 10,000 ($26,500) Bahraini dinars. Fifty-six of those convicted were stripped of their Bahraini citizenship.

The court said those convicted had been smuggling weapons and running training camps in Bahrain with a view to carrying out terrorist attacks.

The terrorist cell was alleged to have been set up in late 2012 and authorities said they uncovered it a year later at the end of 2013.

The court said weapons had been smuggled from “outside” the country, but did not mention from where.

Bahraini authorities – who have been battling a protest movement since 2011 – have regularly accused Shia opposition groups of being backed by Iran, allegations which have been roundly rejected by those involved in calling for democratic reforms in the Gulf kingdom.

Bahraini activists condemned the 56 citizenship removals, alleging that the majority of those convicted will now be left stateless.

“The ruling shows how Bahrain’s justice system functions,” said Sayed Alwadaei, director of advocacy at the London-based Bahrain Institute for Rights and Democracy. “The majority, if not all the 56 individuals stripped of their citizenship, will now be left stateless.”

“This ruling is the harshest punishment the court could have made, with regards to the arbitrary revocation of citizenship.”

The 1963 Bahraini Citizenship Act includes a provision to remove citizenship from anyone involved in “harming the interests of the kingdom or behaving in a way that contradicts the duty of loyalty toward it".

Since the beginning of the uprising in 2011, Bahraini authorities have removed the citizenships of scores of people involved in protests. In November 2012, 31 opposition figures had their Bahraini citizenship withdrawn, including former MPs Jawad Fairouz and Jalal Fairouz.

Thursday’s convictions will be subject to appeal.