The cholera outbreak in Zimbabwe is "the greatest threat ever to face" the country, opposition leader Morgan Tsvangirai says.
His warning came after health officials said the outbreak, which according to the United Nations has killed 360 people since August, was under control.
"The humanitarian crisis that is now engulfing all Zimbabweans represents the greatest threat ever to face our country," Mr Tsvangirai said in a statement reported by AFP.
He also said the toll could rise as the rainy season got under way.
Deputy Health Minister Edwin Muguti earlier said the outbreak was under control and blamed the situation on Western sanctions against Mr Mugabe.
In South Africa, where some Zimbabweans have been treated, Health Minister Barbara Hogan also described the situation as a humanitarian crisis and the country would not prevent Zimbabweans from seeking treatment.
"Under no conditions would we want to stop entry of any person who is ill crossing from Zimbabwe to South Africa," she said. "These are people who need our help. They are our neighbours."
Aid agency Oxfam earlier called on Zimbabwe's government to declare a national health emergency - a call rejected by the government.
Mr Tsvangirai said talks on a power-sharing deal with President Robert Mugabe's party had stalled.
Mr Mugabe's Zanu-PF and the opposition Movement of Democratic Change are in a stand-off following disputed presidential elections earlier this year.
They have agreed to form a government of national unity but have been unable to agree on who should fill key ministries.