Hichilema, an economist and wealthy businessman known as “HH”, was defeated by President Edgar Lungu in an election last August, which he described as fraudulent. His attempts to mount a legal challenge have so far been unsuccessful.
On Tuesday Hichilema was taken in for questioning after his house was raided by the police.
“They have detained him for having committed treason along Limulunga road by obstructing the presidential motorcade,” his lawyer Jack Mwiimbu told Reuters.
“We are definitely challenging the police action. We expect a formal charge tomorrow morning.”
Police did not say why they had detained Hichilema.
“Obviously he will remain in detention,” police spokeswoman Esther Mwaata Katongo told Reuters without elaborating.
A spokesman for Hichilema’s United Party for National Development (UPND), Charles Kakoma, said police broke doors before raiding the opposition leader’s house in an exclusive suburb of Lusaka.
He said police had blocked the access road to the residence but did not say what they were looking for.
“They broke the doors and teargassed the house,” Kakoma said. “They left the home after picking him.”
Mwiimbu said Hichilema was unwell after the raid.
“He is not well because of the tear gas. His wife fainted three times last night because of the tear gas,” he said.
On Sunday, presidential spokesman Amos Chanda said Hichilema had obstructed Lungu’s motorcade, saying Hichilema’s motorcade maintained its lane instead of getting off the road.
Hichilema was granted bail in October after being charged with sedition, a move his team said was an attempt by the ruling party to silence dissent.
The opposition leader had been accused of assembly without a permit after he gave an impromptu address in the rural town of Mpongwe, police said.