Authorities in Bahrain say they have identified and arrested leading members of the Shia opposition February 14 Revolution Youth Coalition, an influential cyber-group accused of working against the government and having links to Iran.
In making the arrests, the country's interior ministry accused the opposition on Thursday of taking part "in criminal acts" and "terrorist" activities.
The February 14 Coalition has been the main force behind a Shia-led uprising that began in 2011 to demand more rights from the country's ruling Sunni leaders.
The ministry identified the group's spiritual leader as Hadi al-Mudaressi, a leading Shia cleric living in the Iraqi holy city of Karbala.
The ministry said he "provided divisive sectarian support to the organisation".
It named 11 of those arrested, saying they had played prominent roles in the coalition inside Bahrain, and said other members were still being sought.
Sentenced in absentia
The ministry also named 13 people that it said were leading the coalition from abroad, some of whom are based in London.
Among those, it said, is Saeed Abdulnabi al-Shahabi "who is responsible for coordination with Iranian leaders".
Shahabi is an opposition leader who has been sentenced to life in prison in absentia for his role in the 2011 uprising.
"They frequently travel between Iran, Iraq and Lebanon to obtain financial and moral support as well as weapons training," the ministry statement said.
These members contact leaders in Iran "to receive direct financial support and field instructions".
"The information presented shows the active role in incitement and terror acts and the support that is provided by extremist religious and political leaders from outside and inside Bahrain," said the statement.
In one of the highest profile cases, Ali Abdulemam, a Bahraini blogger, who was also sentenced to a long prison term, managed to slip out of the country, and sought asylum in England.
Bahrain also accused Lebanese Shia movement Hezbollah - listed as a "terrorist organisation" by the kingdom -- and "extremists" in Iraq of interfering in its internal security affairs.
Tehran, which has repeatedly criticised the kingdom's crackdown on protesters, denies it is backing the uprising.
Bahrain's Shias, mainly in response to calls by the February 14 Coalition, continue to demonstrate in their villages, frequently clashing with police.
A total of 80 people have been killed since the protests erupted in 2011, according to the International Federation for Human Rights.