Just hours after being released by police following five hours of questioning, Morgan Tsvangirai, leader of the main opposition Movement for Democratic Change, told a rally he would apply to the authorities to march through the capital Harare.

Earlier a magistrates court upheld a police ban on the party's application to march on Wednesday, but allowed the opposition to hold a rally. The police had said that street protests could turn violent.

Some MDC youths were involved in skirmishes with riot police as they walked to the venue of the rally. Witnesses said police beat some of the supporters and threw tear gas to disperse them.

Tsvangirai wants President Robert Mugabe to adopt a new constitution ahead of the polls. His party says it will boycott them if it was not satisfied they would be free and fair.

"This is a journey we have started," he told about 3,000 supporters at the rally as riot police watched from a distance.

"The law allows us to demonstrate and tomorrow I want to go back and apply (again)."

Critics say Mugabe, who has ruled the country since independence from Britain in 1980, has used tough security laws to keep his opponents in check. Mugabe denies the charge.

"It is ZANU-PF's character to respond to the peaceful expression of the people through violence and defiance of local and international opinion," Tsvangirai said.

"The law doesn't count in Zimbabwe. As MDC we are committed to the equal and fair application of the law, not what (the ruling party) ZANU-PF is doing."

RESTRAINT

Human rights group Amnesty International urged Zimbabwean authorities to allow protesters to express their opinions.

"The (Police Commissioner) Augustine Chihuri, must ensure that officers under his command exercise restraint when dealing with public demonstrations," said Simeon Mawanza, Amnesty's researcher on Zimbabwe.

"The fact that there have already been assaults and three arrests -- including of a leader of the planned protests -- is a worrying sign," he said in a statement.

About two dozen police in a truck had deployed in front of the MDC headquarters, said a Reuters witness.

Tsvangirai was picked up at 4 a.m. (0200 GMT) from his home in a suburb of Harare by plain-clothes officers for questioning about Wednesday's demonstration. He was released about four hours later, MDC secretary general Tendai Biti said earlier.

Police also picked up another MDC leader, Dennis Murira, who was also released later, Tsvangirai's lawyer said.

Tsvangirai was last arrested in March 2007 along with dozens of opposition officials ahead of another planned march. He says police beat him up in custody but they deny this.

Nelson Chamisa, MDC spokesman, told journalists after the rally that the opposition planned more demonstrations from next week. He did not elaborate.

The police had initially granted permission for Wednesday's march, which the MDC also called to protest against a crumbling economy blamed on government mismanagement.

Zimbabweans have tended to shy away from demonstrations in recent years, mainly from fear of a heavy-handed response by security forces and were on Wednesday busy queuing for cash at banks while many went about their normal business.