South Africa has become the second African country to announce that it plans to leave the International Criminal Court, a decision that campaigners for international justice say could lead to a devastating exodus from the embattled institution.

The move on Friday came three days after Burundi’s president signed a decree making his country the first to withdraw from the court, which had planned to investigate political violence that followed the president’s decision last year to pursue a third term.

“There is a real chance that there will now be large-scale African withdrawals,” said David L. Bosco, an associate professor of international studies at Indiana University who has written a book on the court. “The Burundi decision was easy to dismiss as a government seeking to avoid direct scrutiny; South Africa’s is much more significant. The African Union has been a forum for anti-I.C.C. sentiment, and countries like Kenya and Uganda may now seek to capitalize on the momentum.”

Henry Oryem Okello, a Ugandan minister, told The Associated Press on Friday that his country was “undecided” about whether to remain in the court, and that the “hot issue” of African participation might be taken up at an African Union summit meeting in January.