Hundreds of South Koreans have gathered in Seoul to protest the arrest of a labor union leader who may face a rarely used sedition charge over the eruption of violence at an earlier anti-government protest.

The demonstration on Saturday is the latest in a series of mass protests in recent months of conservative President Park Geun-hye, who has been criticized for her increasingly harsh treatment of union members and dissidents.

The government has clamped down on labor and civic groups involved in organizing a huge demonstration on Nov. 14, when dozens were injured in a clash with police.

Prosecutors are considering indicting arrested Korean Confederation of Trade Unions President Han Sang-gyun for sedition, a charge unseen in South Korean courts since the 1980s when the country was under military dictatorship.