Lawyers representing Zimbabwe's opposition leader Morgan Tsvangirai concluded the bulk of their case Thursday demanding his release on bail.
Defense lawyer George Bizos said state prosecutors provided no evidence that Mr. Tsvangirai had called for the overthrow of President Robert Mugabe.
Mr. Bizos said the state's case consisted of vague allegations and that the real reason Mr. Tsvangirai is being detained is that the government wants "to remove from society an important player" in Zimbabwe.
He said, "It is too convenient a tool against political opponents to keep them in jail on unproved allegations."
Mr. Bizos, a member of the legal team that defended former South African President Nelson Mandela 40 years ago, said the MDC leader's continued imprisonment revived memories of detention without trial in the apartheid era in southern Africa.
Treason charges carry a possible death sentence. On Friday the state will present details of its allegations to try and keep Mr. Tsvangirai in prison until July 12.
Meanwhile, an opposition spokesman said Thursday scores of activists and ordinary supporters remain in police cells following last week's protests.
The police refused to take telephone calls to confirm the numbers still being held.