Zimbabwe's opposition party says its leader, Morgan Tsvangirai, has been released from police custody after several hours of detention.
The opposition Movement for Democratic Change party said police released Mr. Tsvangirai without charge after holding him for eight hours Wednesday at a rural police station north of the city of Bulawayo in the town of Lupane.
It says Mr. Tsvangirai had been campaigning in the area when police stopped his convoy.
A lawyer for Mr. Tsvangirai, Job Sibanda, said police accused the opposition leader of addressing a rally of supporters without authorization.
The United States called Tsvangirai's arrest "deeply disturbing news." Both the U.S. and the European Union called on Zimbabwe officials to immediately release him.
Mr. Tsvangirai is running against President Robert Mugabe in a presidential runoff on June 27. His detention was the latest event in a pre-election crackdown on political activity.
On Tuesday, international aid agencies said Zimbabwe's government had ordered some groups to suspend their work because of alleged political activity. A spokesman for CARE International told VOA the government accused its staff of distributing brochures for the opposition. He denied the charge, saying the aid group has strict policies against political involvement.
Human Rights Watch accused Zimbabwe's government Wednesday of using food as a political weapon in its campaign to win the presidential run-off election.
Before his arrest Wednesday, Mr. Tsvangirai told VOA that the army had seized control of large parts of the country and was blocking the opposition from campaigning there.
Human rights groups and MDC officials have accused Mr. Mugabe's supporters of killing and brutalizing opposition activists in the run-up to the voting. The president denies the charges and accuses the MDC of carrying out its own attacks.
British Prime Minister Gordon Brown said Wednesday he is working with African leaders to try to get international observers into Zimbabwe to ensure the election is free and fair. Zimbabwe's government has in the past said it will only allow observers from friendly countries.
Some information for this report was provided by AFP, AP and Reuters.