JOHANNESBURG, South Africa (CNN) -- Zimbabwe authorities Tuesday released nearly all of the opposition supporters who were detained last week, a Movement for Democratic Change lawyer said.
Tendai Biti, the Movement for Democratic Change's secretary-general, is to address the U.N.
More than 200 opposition supporters were picked up on Friday during raids on the MDC -- the main opposition party -- and Zimbabwe Election Support Network (ZESN) offices in the capital, Harare.
Authorities released 29 people on Friday shortly after they were picked up, MDC lawyer Andrew Makoni said. Another 182 were released on Tuesday, and three remain in detention, he said.
The three still held had been accused of involvement in post-election skirmishes.
The release comes hours before the U.N. Security Council is scheduled to hear from MDC secretary-general Tendai Biti on the country's post-election violence and humanitarian crisis.
Zimbabwe is under international pressure to release the results of its March 29 presidential election. The country's Electoral Commission says it is recounting the votes in the close race, raising the possibility of a run-off between President Robert Mugabe and MDC challenger Morgan Tsvangirai.
The MDC has accused the 84-year-old incumbent and his supporters of staging a carefully orchestrated plan to remain in control of government and weed out opposition supporters by intimidation.
At Tuesday's U.N. hearing, Biti will present evidence the party believes shows Zimbabwe's deteriorating political climate and a government trying to hold on to power, said George Sibotshiwe, a spokesman for Tsvangirai.
"We are trying to find a way forward," he told CNN.
Last week, Biti said the MDC would ask the U.N. "to send in an envoy" and ask the African Union "to call an extraordinary summit" on the situation.
On Friday, hundreds of armed police raided MDC's main office in Harare, seizing computers and documents and arresting more than 300 -- including many refugees who had fled the countryside -- Biti said.
He said those arrested included "pregnant women and very young children, babies. Those arrested also include key members of staff, and some of our politicians."
Biti said the information came from eyewitnesses. A journalist who asked not to be named because of threats to his safety, said police took several people from the MDC office who were "limping and in pain."
Zimbabwe police spokesman Wayne Bvudzijena earlier told CNN that police picked up 200 people at MDC headquarters, known as Harvest House.
"We haven't arrested them officially. We are busy screening them and keeping those whom we are interested in," he said.
On Friday police also raided offices of the ZESN -- an independent election observation group -- in Harare, according to a program manager for the group.
Several police officers arrived with a search warrant looking for "subversive material," a ZESN official said. The police were "taking away documents and CDs, anything to do with our activities," Tsungai Kokerai said.
ZESN is a group of non-governmental organizations that monitored Zimbabwe's March 29 elections. In lieu of official results, ZESN released exit polling data that showed Tsvangirai leading with more than 49 percent of the vote -- short of the 50 percent plus one vote needed to avoid a run-off election.
According to the group's data, Mugabe was second with 41.8 percent and independent candidate Simba Makoni garnered 8.2 percent of the vote.
The Zimbabwe Electoral Commission has repeatedly postponed announcing results of the presidential vote, but Tsvangirai declared victory over the long-time leader based on vote counts posted outside polling stations. E-mail to a friend