The ex-Soviet Central Asian country handed life sentences to two leading figures in the Islamic Renaissance Party of Tajikistan (IRPT) while 11 others received up to 28 years, officials in Dushanbe told AFP, speaking on condition of anonymity.
Tajikistan has not yet released an official statement on the outcome of the closed trial at the supreme court.
Savrinisso Dzhurabekova, wife of one of the jailed men, confirmed to AFP that "two have been sentenced to life" including her husband Makhmadali Khait, the deputy head of the party.
Khait is known for "his vocal support for human rights, freedom of expression, and freedom of religion," Steve Swerdlow, Central Asia researcher at Human Rights Watch, said last month.
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In April, the US State Department labelled Tajikistan a "country of particular concern" over the growing crackdown on Islam in the majority-Muslim country.
The men who were arrested in October last year and went on trial in February, were accused of attempting to seize power by force and "terrorism" over deadly clashes last September.
Afterwards, Tajikistan banned the Islamic Renaissance Party of Tajikistan as an "extremist terrorist organisation," although the party has denied any involvement in the violence.
The party was widely viewed as moderate and was legally registered until the ban. It was seen as one of the few potential sources of genuine opposition to President Rakhmon's two-decade rule.
Critics have called the high-profile trial part of attempts by the government to eradicate Islam from public life.