Zambian opposition leader Hakainde Hichilema was freed from prison on Wednesday after the state prosecutor dropped charges of plotting to overthrow the government, but a judge warned him he could be arrested again at any time.
Mr. Hichilema and five others were arrested in April and charged with treason after his convoy failed to make way for President Lungu's motorcade. His release could help defuse tensions in the southern African country, where Mr. Lungu imposed a state of emergency in July.
High Court judge Charles Chanda told Hichilema and his co-accused that the prosecutor had terminated the proceedings but their discharge was conditional.
"This is not an acquittal as you can be arrested any time over the same offense. For now you are free to go home," he said.
Hichilema's supporters were jubilant, but he showed no emotion as he listened to the judge. He then drove from prison to the headquarters of his United Party for National Development (UPND) in an open-roof Toyota Land Cruiser and waved to supporters over the 5 km (3 miles) stretch.
In a speech outside the building, he called on the government to free several members of the party who are still detained over various charges.
"As of yesterday, some of our members were arrested. Even today, as I speak, others were arrested," Hichilema told hundreds of supporters, without giving details of the cases.
"Zambia's criminal justice system has broken down. I can't say I am free when our members are in detention," Hichilema said, adding, "I am willing to go back to prison" if the arrests persisted.
Hundred of people celebrated outside the prison, singing, dancing, and waving red and yellow UPND flags. Others marched outside the party's headquarters, shouting Hichilema's name and punching the air in victory.
"It is good he is out, but sad that he has been released conditionally. We would have loved him to be acquitted," said Peter Simukonda, a 26-year-old University of Zambia student.
After the initial treason charge over the motorcade incident, Hichilema was later accused of plotting to overthrow the government.
The case has heightened political friction in Zambia, a major copper producer which is seen as one of Africa's more stable democracies, after a bruising election last year in which Lungu's Patriotic Front defeated Hichilema's UPND.
A government spokesman said the release of Hichilema showed the state did not interfere with the courts.
"We accept what has happened today and respect the decision of the DPP," chief government spokeswoman Kampamba Mulenga said. "This shows that the government does not interfere with the judicial system."
Hichilema, an economist and businessman widely known as HH, mounted an unsuccessful legal challenge claiming the poll was rigged. His release could ease tensions in the run-up to elections in 2021, analysts said.
"It signifies the beginning of the reconciliation process, with the next elections being central," said Alex Ng'oma, a political science lecturer at the University of Zambia.
Government and legal sources had told Reuters on Sunday that Zambia's government would drop the treason charges and free Hichilema under a deal brokered by Commonwealth Secretary-General Patricia Scotland.
Ms. Scotland visited Zambia last week and told reporters she had met Lungu and Hichilema separately and that the two leaders had agreed to a process of dialogue facilitated by her office.
In a statement, Scotland said she hoped the decision to drop charges would help Zambia "achieve political cohesion and reconciliation through dialog."
A Zambian official said the Commonwealth would be appointing a special envoy to facilitate the talks between Lungu and Hichilema along with other political players.
Last month Lungu invoked emergency powers to deal with "acts of sabotage" by his political opponents after fire gutted the country's biggest market. The powers allow police to ban public meetings, detain suspects longer than usual, search without a warrant, close roads, impose curfews, and restrict certain people's movements.
This story was reported by Reuters.