Some of the 700,000 Zimbabweans hit by slum clearances are living in "very bad" conditions, said a top UN envoy after visiting a squatter camp.
The visit comes amid Zimbabwe's worsening economic crisis
UN's emergency relief co-ordinator Jan Egeland waded through mud to meet people living under plastic sheets, reports Reuters news agency.
This is the highest level visit since a UN report condemned the demolitions.
Mr Egeland was invited to "correct" the bias of that report, said Zimbabwe's President Robert Mugabe.
"It is very clear that the needs are great, the needs are tremendous and the people are living under very bad conditions," Mr Egeland said after visiting the Hatcliffe camp 20km outside the capital, Harare, home to about 8,000 people.
Reuters reports that women ululated and cheered when they saw Mr Egeland, hoping his visit might lead to better living conditions.
He later went to Whitecliff, where the government says it is building new houses for some of those made homeless.
The government had refused international help for those affected - saying far fewer than 700,000 were affected.
The evictions have left hundreds of thousands of people homeless
But last month, it accept the offers of aid and has also reached an agreement to let the World Food Programme distribute aid to at least three million people going hungry after poor harvests.
The government said the slum clearances were intended to reduce crime and overcrowding.
Mr Egeland is due to meet Mr Mugabe on Tuesday. He met Local Government Minister Ignatius Chombo and other government officials over the weekend.
The visit follows a UN report describing Zimbabwe as being "in a virtual state of emergency".
It said forced government evictions of hundreds of thousands of people earlier this year had deepened the country's economic problems.
The report, compiled by Anna Tabaijuka said the forced evictions had caused untold misery.
Mr Egeland will assess the performance of UN agencies in their efforts to help Zimbabweans through the worsening crisis.
He is also due to meet religious and civil society leaders, some of whom are bitterly critical of the government.
In southern Zimbabwe, Mr Egeland is expected to travel into rural areas where people are suffering severe food shortages.
Zimbabwe has blamed recent droughts for the poor harvest
Last week lobby group Human Rights Watch said that since Mrs Tabaijuka's report, UN agencies in Zimbabwe have not done enough to help destitute people and have been reluctant to confront Mr Mugabe's government.
A senior UN official in the region told the BBC that the agencies are "caught between a rock and a hard place".
They have an obligation to maintain a presence in Zimbabwe and, he said, they cannot achieve much without collaborating with Mr Mugabe.
The BBC's Barnaby Phillips says Mr Egeland will get a better understanding of this awkward dilemma for the UN - to concentrate on humanitarian work or confront the government but risk losing all influence.