Lusaka - Zambia's detained opposition leader Hakainde Hichilema is due to appear in court on Monday on treason charges, four months after he was arrested and as political tensions rise in the country.
Hichilema, who narrowly lost last year's presidential elections, has been in custody since April over an incident when he allegedly failed to give way to President Edgar Lungu's motorcade.
A lawyer from his United Party for National Development (UPND) told AFP that the party expected the charges to be dropped and for Hichilema to walk free.
"They don't have a case against him. We are certain that he will come out tomorrow," the party lawyer, who declined to be named, told AFP on Sunday.
Lungu invoked emergency powers in July, increasing police powers of arrest and detention after he blamed opposition parties for a string of arson attacks.
The president has denied allegations of growing authoritarianism and has accused his rivals of trying to overturn the election result.
Hichilema, 55, says the election was rigged and has refused to recognise the president.
Zambia has enjoyed relative stability since its first multi-party election in 1991.
But last year's election was marked by clashes between supporters of Lungu's Patriotic Front (PF) party and the UPND.
Parliament has suspended 48 UPND lawmakers after they boycotted an address by Lungu in March.
Police on Thursday released the leader of a smaller opposition party who is a fierce critic of the president after one week in detention.
Savior Chishimba, leader of the United Progressive Party (UPP), was detained by plain-clothed police, triggering further accusations of a crackdown on dissent.
Hichilema has been held in custody after allegedly putting Lungu's life in danger when his convoy failed to make way for the presidential motorcade in a high-speed road drama caught on video camera.
'I will sacrifice democracy for peace'
The two men were both travelling to Western province for a traditional ceremony.
Days later, more than 100 armed police surrounded Hichilema's house outside Lusaka, firing tear gas before detaining him.
Businessman-turned-politician Hichilema has claimed that he was assaulted by police during his arrest and has suffered mistreatment in detention.
Treason is a non-bailable offence in Zambia, with a minimum jail term of 15 years and a maximum sentence of death.
Lungu did not mince his words during the election campaign, warning political rivals and activists that "if they push me against the wall, I will sacrifice democracy for peace".