The outbreak of cholera in Zimbabwe has flared up once again, with more than 1,000 new cases reported in a single day, the United Nations has said.

According to the World Health Organisation, the outbreak had recently shown signs of slowing but is now once again on the rise.

On Tuesday, 1,080 new infections were reported, with 21 people dying.

More than 1,700 people have died since the beginning of the cholera outbreak in August last year, with about 35,000 infections across the country.

The rapid spread of the waterborne disease has been blamed on the collapse of Zimbabwe's health and sanitation infrastructure.

Human rights groups say the humanitarian crisis has been exacerbated by the refusal of Robert Mugabe, the Zimbabwean president, to acknowledge the extent of the problem.

Last month, Mugabe said the cholera outbreak was being used as an excuse by Western powers such as Britain to invade Zimbabwe and overthrow him.