Seventy alleged mercenaries held in Zimbabwe have been charged with conspiring to murder the president of Equatorial Guinea.
The plane has been moved to a Zimbabwean military base
They have already been charged with trying to buy weapons illegally and violating Zimbabwe's immigration laws.
Zimbabwe has accused them of planning a coup in Equatorial Guinea.
The men - who deny the charges - have been detained for the last 10 days since their plane was impounded in the Zimbabwean capital, Harare.
The men's lawyers have described the new charges as "fictional".
They said that if any conspiracy had taken place it would have been in South Africa, where the men started the flight and where they are all from.
"This is really a fictional charge. I would not want to
speculate at this point what the penalty would be," lawyer Jonathan Samkange said.
A government minister has said the men could face the death penalty.
They have not yet appeared in court and the BBC's Alastair Leithead in South Africa says the new charges are expected to add further delays.