Stripped of nationality: Bahrain's escalating crackdown on opposition
The defendants were convicted of "establishing and raising donations to fund a terror organisation named Bahraini Hizballah", according to a judicial source.
Authorities say the group attempted to kill police officers in Nuwaidrat, a village east of Manama, during what was described as an unauthorised demonstration.
In a separate hearing, 13 others were also sentenced to 15 years each after being accused of attacking a police patrol with Molotov cocktails.
Some 22 others were jailed for three years each in that same case, while five others were acquitted, a prosecution statement said.
UN Secretary-General Ban Ki-moon voiced concern over Bahrain's escalating crackdown against its opposition.
He said he was "dismayed" by reports that human rights activists had been intimidated and stripped of their citizenship, a UN statement said.
Ban said "the current actions against the opposition may undermine the reforms undertaken" and "lessen the prospect of an inclusive national dialogue in the interest of all people of the kingdom".
The latest crackdown on opposition members follows similar moves just days ago.
On Tuesday, Bahrain suspended activities of the main Shia-dominated opposition group, raising concerns in the Sunni-ruled kingdom as well as among international rights defenders and officials in Washington.
A Bahraini court suspended the Al-Wefaq group pending a verdict on dissolving it altogether, the justice ministry said, accusing the bloc of breaking the law.
The decision came a day after security forces rearrested leading human rights activist Nabeel Rajab, drawing a complaint from the United States.
The court also ordered Al-Wefaq offices closed and its funds frozen, said a justice ministry statement published by the official Bahrain News Agency (BNA).
Al-Wefaq draws most of its support from the Shia majority in the small kingdom across the Gulf from Shia Iran.
|The Bahraini government seems determined to kill all avenues of peaceful dissent
The bloc's chief, Shia cleric Ali Salman, is currently serving a nine-year jail term for inciting violence after a court last month more than doubled his original sentence.
Salman's arrest in December 2014 sparked protests in a country already rocked by a Shia-led uprising that erupted in February 2011.
Tuesday's ruling followed a justice ministry request for Al-Wefaq to be dissolved for alleged illegal activity.
The bloc was accused of offering a haven for "terrorism, radicalisation, and violence" and opening the way for "foreign interference" in the kingdom's affairs, the ministry said.
This was a reference to Iran, which Bahrain accuses of fomenting unrest on its soil by backing the Shia opposition.
The Washington-based group Human Rights First in a statement on Tuesday called Al-Wefaq's suspension "part of an alarming new crackdown by the government, designed to eliminate all remaining opposition in the country".
"The Bahraini government seems determined to kill all avenues of peaceful dissent. This is a dangerous course, and is likely to fuel extremism and deepen political instability," said the group's Brian Dooley.
Human Rights First on Tuesday urged the US government "to hold its ally Bahrain accountable for its human rights abuses".