Two Zimbabwean opposition activists who were seeking medical treatment abroad after allegedly being beaten by police were among three detained trying to leave the country, a party official said. The African Union, meanwhile, called on Zimbabwe to respect its citizens' human rights. Arthur Mutambara, head of a faction of the main opposition Movement for Democratic Change, was arrested by police at Harare International Airport as he was leaving for South Africa on Saturday, said Roy Bennett, the movement's exiled treasurer-general. Also arrested in a separate incident were Grace Kwinje and Sekai Holland, who were to receive specialized medical treatment in South Africa, he said. "We are not sure why they were arrested. Tensions are very high," he said. Tawanda Mutasah, director of the Open Society Initiative for Southern Africa, said the two women, among the most severely injured when Zimbabwean police broke up a protest gathering Sunday, were due to travel to Johannesburg to receive specialist post-traumatic care. He said the ambulance carrying the women from Harare's Avenues clinic to the airport, where they were to leave in a medical rescue aircraft, was stopped on the tarmac by officers from Zimbabwe's security forces. The women's passports were taken and they were told they needed a clearance certificate from the Department of Health. They were then instructed to go to Harare's central police station but were later allowed to return to the clinic under police guard. "That the Zimbabwean government now resorts to arresting people in ambulances in clear need of specialist care, is an indication of the repressive lengths they're prepared to go," said Mutasah, adding that lawyers for the women were trying to get a court order to allow them to receive treatment. Bennett also said that, according to reports from Harare, police took the body of Gift Tandare, an activist shot dead by police, and performed their own burial. Tandare's father was forced to release his son's body into police custody while family were preparing for the funeral, he said. Zimbabwean police used tear gas, water cannon and live ammunition to crush the March 11 gathering, and beat activists, including the main opposition leader Morgan Tsvangirai, during and after arrests, according to opposition members. AU Commission chief Alpha Oumar Konare "has followed with great concern the recent developments in Zimbabwe" and "recalls the need for the scrupulous respect for human rights and democratic principles in Zimbabwe," the 53-nation bloc said in a statement. African nations have been criticized for their failure to speak out against Zimbabwe President Robert Mugabe's treatment of the opposition. Tsvangirai left the hospital Friday battered but defiant, pledging to "soldier on until Zimbabwe is free." His supporters vowed to drive Mugabe from office with a campaign of civil disobedience. Mugabe warned his opponents against inciting unrest. "If they do it again, we will bash them again," he said in an address to his party's youth wing, state radio reported. The latest violence has drawn new attention to a deteriorating situation in the southern African country, where the increasingly autocratic Mugabe is blamed by opponents for repression, corruption, acute food shortages and inflation of 1,600 percent - the highest in the world.