Activists launched a hunger strike Wednesday to demand faster political change in Zimbabwe and urge African leaders to isolate the country's president, Robert Mugabe, who is accused of overseeing its political and economic collapse.

The South African and Zimbabwean activists also hope thousands in the region will join them in a series of fasts over the next three months.

Wilson Mugabe, a pastor from Zimbabwe who is not related to its president, said he would go for a week without water or food and camp out at a Johannesburg church that has been a refuge for Zimbabweans fleeing political oppression and economic collapse.

The church, draped Wednesday in anti-Mugabe banners as well as the drying laundry of the hundreds of Zimbabweans living there, will be the headquarters for the hunger strike.

The pastor said he sent his family into hiding before coming to Johannesburg for fear the protest would prompt attacks by Zimbabwe's government.

"We have suffered enough," Wilson Mugabe said, breaking into tears. Others at the podium started up a chant of "Viva Pastor Mugabe!"

Kumi Naidoo, a veteran of the anti-apartheid movement, began a 21-day, water-only fast Wednesday, while retired Cape Town Archbishop and Nobel laureate Desmond Tutu, long among Robert Mugabe's sharpest critics, will fast one day a week. Tutu is 77.

Human rights activist Graca Machel, who is also the wife of former South African President Nelson Mandela, attended the launch at the church but the 63-year-old said she would not be fasting for personal reasons.

The activists said their Zimbabwe campaign would include protests at a regional summit Monday in South Africa or Botswana, which has been called to try to push Mugabe and opposition leader Morgan Tsvangirai to enact a power-sharing deal they signed in September.

The deal has been stalled in a dispute over how to share Cabinet posts, and by what the opposition and independent observers call Mugabe's growing, violent crackdown on dissent.

Mugabe has been in power since Zimbabwe gained independence from Britain in 1980.

Machel, speaking on a panel that included three clergyman, slipped into the cadences of a preacher herself and was greeted with applause and shouts of affirmation reminiscent of a revival meeting. She described the beatings, rape and killings of dissidents in Zimbabwe.

"Any government who goes out and assaults its own citizens, its own people, has lost completely any kind of legitimacy," she said.

Tutu has urged the international community to use the threat of force to oust Mugabe. Asked Wednesday whether Mugabe should step down, Machel said: "The people of Zimbabwe have already said so — through the ballot."

Tsvangirai won the most votes in a presidential election held almost a year ago, then dropped out of a June runoff against Mugabe because of attacks on opposition supporters.

The political standoff has kept Zimbabwe's leaders from addressing their country's economic collapse, which has led to a cholera epidemic and left millions of Zimbabweans depending on international food aid.

Machel and the other activists said Wednesday that mediation efforts led by South Africa have taken too long and yielded too little.

"It's hard for someone to have to admit that I have been part of those who trusted ... that our leaders knew what they were doing, that our leaders would find a solution," she said. "We stood and waited too long. Today, I'm here to stand and be counted among those who say, `Enough is enough."'

Machel and Tutu are both members of The Elders, an international team of statesmen founded by Mandela and including former U.S. President Jimmy Carter, who to try to find solutions to global crises. In November, Mugabe's government barred The Elders from making a fact-finding tour of Zimbabwe.