Almost all the 70 mercenaries accused of plotting to overthrow the government of Equatorial Guinea have pleaded guilty in a Zimbabwe court.
The men have been held since March
The 67 South Africans admitted the lesser charges of breaking immigration and aviation laws at their much delayed trial in the capital, Harare.
All 70 are expected to face further security charges on Wednesday.
Their plane was impounded in March, when they picked up weapons bought from the Zimbabwe state arms supplier.
Three men, including former British SAS captain Simon Mann, the alleged leader of the group, did not face the immigration charges because they were already in Zimbabwe when the plane landed.
The start of the trial was twice delayed while the defendants reviewed the charges with their legal advisors.
Defence lawyer Jonathan Samkange said all 70 would plead not guilty to more serious charges of breaching security on Wednesday.
The group said they were going to the Democratic Republic of Congo to provide security for mining operations.
But the governments of South Africa, Zimbabwe and Equatorial Guinea believe they were heading to the small, oil-rich country to overthrow the government.
The BBC's Alastair Leithead in Johannesburg says there is much confusion surrounding the alleged coup plot and how the men came to be arrested.
This is the first time they have faced formal charges, even if they are relatively minor compared to the gravity of the accusations, our correspondent says.
The trial is being held in a building inside a high-security prison surrounded by high concrete walls and razor wire.
The men, who have been held for four-and-a-half months with restricted access to lawyers and relatives, have complained about prison conditions.
Following their arrest in March, they had claimed they were tortured by Zimbabwean security agents.
The Zimbabwean government recently signed an extradition deal with Equatorial Guinea, where other South Africans are being held on suspicion of being the advanced party in the alleged plot.
The group's lawyers have appealed to the South African government to extradite them there instead, so they would not face a possible death penalty.
But South African state lawyers have opposed this legal request and the constitutional court is to deliver its decision.