Zimbabwe's Prime Minister Morgan Tsvangirai said on Thursday that cases of infections and deaths from the country's worst cholera epidemic were far higher than those reported.

More than 80,000 people have been infected since the outbreak six months ago with nearly 4,000 killed, according to the World Health Organisation.

"This is most likely a dramatic underestimate of the real figures given the unreported cases and deaths in communities," Tsvangirai told an emergency meeting of health officials and donors.

The deadliest cholera outbreak in Africa in 15 years has spread to neighbouring countries, including South Africa.

Zimbabwe's health system has all but collapsed with hospitals battling shortages of drugs, high cases of HIV/AIDS and nurses and doctors frequently on strike for higher pay.