Prominent Zambian opposition leader Hakainde Hichilema has been freed on bail after pleading not guilty to a charge of inciting violence.
He was arrested on Tuesday following the killing of governing party member Harrison Chanda a day earlier.
A crowd allegedly killed Mr Chanda in Livingstone town, ahead of a by-election that has now been postponed.
Zambia is a largely stable democracy, though some violence flares up during elections, correspondents say.
A court in Livingstone freed Mr Hichilema, the leader of the United Party for National Development (UPND), on $400 (£263) bail, reports the BBC's Mutuna Chanda from the capital, Lusaka.
He pleaded not guilty to a charge of inciting violence.
Another seven people have been charged with the murder of Mr Chanda, a youth official in the governing Patriotic Front (PF) party.
He was hit on the head with an axe after being attacked by a group of people in Livingstone on Monday night, AFP news agency quotes police as saying.
The UPND denies its members killed him.
Zambia's election officials said the by-election, which was due to have taken place on Thursday, would be held at a later date to ease tensions, our reporter says.
The by-election was triggered by the resignation of the UPND MP Howard Sikwela.
It was being contested by the PF's Lawrence Evans and the UPND Regina Musokotwane.
The UPND came third in Zambia's elections in 2011.