A senior U.N. envoy urged Zimbabwe on Friday to halt the deliberate destruction of the country's slums and give humanitarian aid workers access to more than 700,000 impoverished people who have been driven from their homes.

Anna K. Tibaijuka, a senior U.N. housing official who recently returned from Zimbabwe, accused the government's military and police forces in a report of destroying thousands of slum dwellings and marketplaces as part of a nationwide campaign to beautify the country's cities. She urged wealthy governments to provide hundreds of millions of dollars in assistance to Zimbabwe's government and to private charities to help victims and rebuild destroyed homes and neighborhoods.

U.N. officials say they hope the prospect of fresh aid will nudge Zimbabwe's president, Robert Mugabe, into reopening talks with the country's political opposition and ending a land-reform program that the report said has crippled the nation's economy.

Tibaijuka, executive director of the U.N. Center for Human Settlement, played down suggestions that Mugabe may have ordered the destruction, saying that the operation was carried out on the advice of a small group of unnamed government officials. Tibaijuka said that although it was not within her mandate to "apportion blame," she has asked U.N. Secretary General Kofi Annan to consider ways to hold accountable those responsible for the destruction.

Annan issued a statement saying the 100-page report shows that the government crackdown has "done a catastrophic injustice" to hundreds of thousands of Zimbabwe's poorest with "disquieting indifference to human suffering."

Annan said that although criticism of Mugabe's government is "fully justified," the international community must turn its attention to "those in need" in Zimbabwe.

"The United Nations will urgently seek agreement with the Government of Zimbabwe to mobilize immediate humanitarian assistance on the scale that is required to avert further suffering," he said.

Mugabe's government launched a massive police and military operation in May to rid Zimbabwe's capital, Harare, and other cities of the slums that it asserts have served as laboratories for crime, black-market trade and other forms of urban blight. Operation Murambatsvina -- or Operation Drive Out the Rubbish -- began May 19 in Harare.

"It quickly developed into a deliberate nationwide campaign, destroying what the government termed illegal vending sites, structures, other informal business premises and homes, literally displacing hundreds of thousands of people," the report said.

The government campaign has virtually "wiped out" Zimbabwe's informal economy, which accounted for 40 percent of the African country's economic activity, increasing hardship for more than 2.4 million of the country's poorest, the report said. Inhabitants of the destroyed slums were told to return to their "rural origins," said the report, which alleged that the government broke local and international law.

Zimbabwe's foreign minister, Simbarashe Mumbengegwi, said in Harare that it is "definitely false" that the government broke laws, according to Reuters. "The report described the operation in vastly judgmental language which clearly demonstrates its inbuilt bias against the operation," he said.

Munyadzi Shuzhu, 1, and brother Peter, 2, sit in the rubble of their family's house in Porta Farm, Zimbabwe, after the government destroyed it.