Zambia's main opposition leader Hakainde Hichilema on Tuesday claimed he was assaulted by police during his arrest as he appeared in court on charges of obstructing the presidential motorcade.
The leader of the United Party for National Development (UPND), who appeared in a magistrate's court, faces multiple charges over the alleged motorcade incident, which occurred on the weekend of April 8-9.
One of the charges is treason, which will be heard at a later date in the High Court.
Police went to arrest him on April 11, with Hichilema telling the magistrate that they had attacked and tear-gassed him in an ordeal lasting 15 hours.
"We were attacked by criminals in police uniforms," he said. "They came without a search warrant."
Hichilema had allegedly refused to give way to President Edgar Lungu's convoy as they were both travelling to the Western province for a traditional ceremony.
Several days later, more than 100 armed police surrounded Hichilema's house outside Lusaka, firing tear gas before taking him into custody, AFP correspondents at the scene said.
His lawyer accused police of using excessive force during the arrest and of "torturing" in custody three of his aides arrested a day earlier.
"The police sprayed pepper spray in their private parts, mouth, ears," lawyer Jack Mwiimbu told the court.
Hichilema has launched unsuccessful legal bids to challenge Lungu's victory in last August's election, and the businessman-turned-politician has said he does not recognise Lungu's presidency.
He claims the vote was rigged and accuses Lungu of unleashing an unprecedented bout of political repression in the southern African country, which is known for its relative stability.
Hichilema's lawyer Vincent Malambo told the court that since his arrest, his client had been denied access to a legal representative and family visits.
At Tuesday's hearing, the magistrate ruled that he be seen by a doctor of his choice and be given access to both lawyers and family while in custody.
His arrest has been strongly condemned by civil group and political commentators who say the charges will fuel tensions.
The presidency meanwhile reacted angrily to comments reportedly made by Nigeria's former president Olusegun Obasanjo appealing to Zambian authorities to follow the rule of law in dealing with Hichilema.
"We find Obasanjo's interference unacceptable," presidential spokesman Amos Chanda told foreign correspondents in Lusaka on Tuesday.
He said Obasanjo was not being "sincere" and accused him and unnamed individuals under the auspices of a Johannesburg-based think-tank, the Brenthurst Foundation, of trying to secure Lungu's removal from power by helping the opposition.
"We cannot take their advice, they can go to hell," said Chanda.
President Lungu has vowed not to interfere in the trial.
Hichilema returns to court on Wednesday.