JOHANNESBURG, South Africa — A high court judge in Zimbabwe on Friday ordered police to produce Tendai Biti, the opposition party’s secretary-general and chief strategist, who was arrested Thursday the moment he re-entered the country and whose whereabouts have since remained a mystery.

“We have sent teams of lawyers to every police station in Harare but have failed to find where they have him,” said Nelson Chamisa, a spokesman for the Movement for Democratic Change. “We are concerned now for his security, his safekeeping, his life; he has fallen into the jaws of danger.”

The police have said Biti would be charged with treason, a capital offense. But the opposition leader has not been seen by associates since he was swiftly handcuffed at Harare’s airport and hustled away.