Human Rights Watch on Thursday urged Bahrain to retract its decision to revoke the citizenship of 31 Shiites for having "undermined state security", describing the move as a violation of basic rights.
The government's action, announced on Wednesday, has also been condemned by Bahrain's opposition as well by other rights groups, among them Amnesty International.
"Bahraini authorities should rescind their announced decision to strip citizenship from 31 people for allegedly damaging the country's security," New York-based Human Rights Watch said in a statement.
"The order was imposed without due process of law and will leave the majority of the people affected stateless," it said.
Bahrain, home to the US Fifth Fleet and strategically situated across the Gulf from Shiite Iran, said it had revoked the citizenship of 31 Shiite activists, among them two former parliamentarians, for having "undermined state security."
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"There is no justification for equating political dissent with damaging Bahrain's security," said HRW's deputy Middle East director Joe Stork.
According to the watchdog, at least 10 of the activists have been living outside the kingdom for years, while only about six have acquired citizenship of other countries. The rest will be left stateless.
"Bahraini authorities have been increasingly targeting opposition activists and this decision takes it to a new level," Stork said.
Bahrain late last month banned all protests and gatherings to ensure "security is maintained," after clashes between Shiite-led demonstrators and security forces in the Sunni-ruled country.
According to the International Federation for Human Rights, 80 people have died in Bahrain since unrest which followed the crushing of Shiite-led protests erupted in February last year.
Tension has been running high following a spate of bombings on Monday in Manama, which killed two Asian expatriates. Four people have been arrested in connection with the bombings.