The court, whose ruling can be appealed, also sentenced another defendant to 10 years. All were stripped of their Bahraini citizenship, the source told AFP.
The main suspect, Murtadha Al-Sendi, who was sentenced to death on Monday, formed two “terror” groups, one of which manufactured explosives and bombs and stored them in hideouts, the judicial source said.
The second group received arms and explosives smuggled from Iran by sea and hid them, the source added.
Seven of the defendants were arrested when security forces broke up the two cells and recovered large quantities of arms and explosives.
Another four suspects are still at large.
The court heard that at least four of the accused were trained in the use of arms and manufacturing explosives in Iran and Iraq.
On Monday, Bahrain’s top military court sentenced six to death and seven to seven years in prison for plotting to assassinate the country’s armed forces chief.
Over the past year, Bahrain foiled several terror attack attempts.