A South Korean court has sentenced an opposition member of parliament to 12 years in jail for plotting a pro-North Korea rebellion.
The move has drawn criticism from rights campaigners who said the government was stifling free speech.
Prosecutors said Lee Seok-ki from the small, left-wing United Progressive Party had gathered information on US bases, communications and a power plant and said he had plotted an armed rebellion in support of North Korea.
It was the first time since democratic elections took place in 1988 that the South's National Security Act has been used against a member of parliament, although Lee, a former student activist, has been imprisoned before.
The Suwon District Court said that although conflict between North and South Korea had not occurred in 2013, the planned revolt was a real danger as the North still has the ambition to unify the two Koreas by force.
South Korea's conservative president, Park Geun-hye, has called for Lee's party, which has six members of parliament, to be banned, triggering accusations from opposition parties that her government was using the trial to cover up complaints that the state intelligence service helped rig her election.
Ms Park has declined to comment on the accusations.
Prosecutors accused Lee of gathering 130 followers in secret meetings last May to plot a rebellion and said he led a group that praised North Korea's ruling Kim family and its political system.
Lee's lawyers said they would file an appeal against the conviction and lambasted the judiciary for what they said was its failure to protect democracy.
There have been small protests against Lee's prosecution since his arrest last September, although the main opposition party appears to have been wary of showing support for him.
Lee's party, which secures about 1% of the popular vote, is seen as supporting the North's political aims.
Outside the court in Seoul's suburbs, opinion was sharply divided.
Special forces veterans in military fatigues shouted "Execute Lee Seok-ki! Execute Kim Jong Un," referring to North Korea's leader.
Across the street in front of the court the party's supporters called for his release and waved purple balloons. Purple is the party's colour.
North Korea threatened to attack South Korea, the US and Japan last year in a barrage of rhetoric that went on for months and saw the United States redeploy military assets in the peninsula.