Zimbabwe opposition leader Mr Morgan Tsvangirai was released by police this afternoon after being charged with contempt of court.
Police earlier arrested him and fired tear gas at student protesters as they set about crushing the launch of widespread anti-government demonstrations.
Mr Tsvangirai, leader of the opposition Movement for Democratic Change (MDC), was arrested at his home and charged with contempt of court for planning an illegal demonstration.
The former trade union leader had become increasingly defiant in his calls for the people to rise up against President Robert Mugabe.
The MDC blames Mr Mugabe and his policies for sinking the southern African country into economic and political chaos. This week it called for its supporters to show their disapproval on the streets.
Riot police fired tear gas at hundreds of students at Zimbabwe University, forcing them back as they tried to march from their campus to the centre of the capital Harare.
Tear gas was also fired at a group that gathered on the street in the Harare township of Budiriro.
In another Harare township, Mabvuku, army trucks packed with soldiers were seen patrolling through the night. Riot police in helmets and bearing clubs stood watch in the city centre.
Mr Tsvangirai appeared in court today where he is standing trial for treason. The state says he was part of a plot to assassinate Mr Mugabe, charges he and his fellow accused - two senior opposition officials - vehemently deny.
"I am in no position to comment," Mr Tsvangirai said of his arrest as he was hurried into court by two plain clothes detectives. Police had tried to arrest him hours earlier, but left when they found he was not at home and were forced to return this morning.
One of his fellow accused, MDC secretary-general Mr Welshman Ncube said police had also tried to arrest him overnight. He was not at home, but police assaulted his staff, he said.
"They beat my workers, there are broken bones," he said.
Of the launch of this week's actions against the government, he said, "it is tough and it is very tense."
As part of their crackdown against demonstrations, police-manned roadblocks were set up along all the main roads leading into Harare and military helicopters swooped over the western city of Bulawayo. Both cities are opposition strongholds.
Agencies