Supporters continue to gather in support of top cleric Ayatollah Sheikh Isa Qassim after the kingdom stripped him of his nationality.
An Iranian Revolutionary Guards commander has warned Bahrain that stripping a top Shia cleric of his citizenship could result in armed resistance across the country.
Dozens of supporters of Ayatollah Sheikh Isa Qassim, spiritual leader of Bahrain's Shia Muslim majority, gathered at his home on Tuesday to protest the revocation of his citizenship, with some men wearing white shrouds signalling their readiness to die
The warning came from General Qassem Suleimani, head of the elite Revolutionary Guards' overseas operations arm, the Quds Force, after Washington also strongly criticised the move by its Gulf Arab ally.
"The Al Khalifa [rulers of Bahrain] surely know their aggression against Ayatollah Isa Qassim is a red line..... that will leave no option for the people but to resort to armed resistance," said Suleimani late on Monday.
"Al Khalifa will definitely pay the price for that, and their bloodthirsty regime will be toppled," the commander added.
Bahrain stripped Qassim's citizenship on Monday amid continuing crackdowns against members of the Shia sect. A court decided last week to ban the main political opposition group al Wefaq.
Bahrain has defended its actions against Shia Muslim figures in the kingdom in the context of national security.
The Bahraini interior ministry alluded to several accusations in its statement announcing the decision against Qassim. Sheikh Qassim abused his position to "serve foreign interests and promote... sectarianism and violence," it said.
Last week Bahraini media reported that authorities initiated an investigation into bank accounts under Qassim's name.
The investigation was to determine where the funds were coming from and how they were being spent.
Qassim had served as a member of the Parliament in the 1970s.
If expelled, he will not get benefits tied with citizenship, such as access to free health care and pension, like many others who are in the same position. Once their passports are revoked, they could be considered as stateless.
Saudi Arabia voiced support for its neighbour, saying it stands by Bahrain in "measures taken to preserve the security, stability and safety of its citizens" and to protect "unity and social cohesion".
The Arab heavyweight has been a strong backer of Manama and repeatedly accused arch-rival Iran of meddling in Bahraini affairs.
The Bahrain Institute for Rights and Democracy said the withdrawal of Qassim's citizenship would stoke unrest.
"We are deeply concerned these actions will escalate tensions on the streets and may even lead to violence, as targeting the country's leading Shiite cleric is considered to be a red line for many Bahrainis," Sayed Ahmed al Wadaei, the institute's director of advocacy, said in a statement.
"We are alarmed by the decision to revoke the citizenship of Shia cleric Sheikh Isa Qassim," US State Department spokesman John Kirby said.
"We remain deeply troubled by the government of Bahrain's practice of withdrawing the nationality of its citizens arbitrarily," Kirby said. "Our concern is further magnified by reports that Sheikh Qassim was unable to respond to the accusations against him... or challenge the decision through a transparent legal process."
The UN human rights office also expressed concern over the "intensified crackdown on the freedoms of expression and association and the right to a nationality." It urged Bahrain's rulers "to de-escalate the situation instead of taking such damaging steps in quick succession."
"Given that due process was not followed, it cannot be justified," Ravina Shamdasani, a spokeperson for the United Nations human rights office, told a briefing in Geneva.
United Nations High Commissioner for Human Rights Zeid Ra'ad al Hussein said at least 250 people in Bahrain have reportedly been stripped of their citizenship by the government because of their alleged "disloyalty to the interests" of the kingdom.