"It's been an ordeal, but we survive. We live to fight another day, I am glad to be home," Tendai Biti told reporters soon after his release.

The United States said it was concerned about reports of detentions, beatings and other abuses targeting opposition activists. It singled out the case of Biti and signalled that Zambia could face consequences for its role in handing him back.

"We will be discussing this matter with Zambia’s leaders and reviewing certain aspects of our cooperation with the Zambian government," the State Department said in a statement.

Speaking in court to lawyers and the media, Biti said he had feared being abducted by the security forces. "They wanted to abduct me. I was terrified," he said.