The men were arrested Tuesday in Limpopo province, The Africa Report.com said. The defendants include one U.S. citizen, James Kazongo, who is originally from the DRC, the U.S. embassy in Pretoria said.
Officials said police launched a sting operation after getting a tip that men planning a coup against President Joseph Kabila were preparing for military training.
At the hearing in the Pretoria Regional Court, Shaun Abrahams, the prosecutor, said the men are members of a DRC opposition group, the Union of Nationalists for Renewal.
"They intended on unseating President Kabila unconstitutionally," Abrahams said.
The men are charged with violating the Foreign Military Assistance Act. Proceedings were postponed for a week to give them a chance to retain lawyers and police time to confirm their identities.
About 100,000 refugees from the DRC are living in South Africa. Most are opponents of the current DRC government.