Residents of Guinea's second-biggest city have rioted after the market was sprayed with disinfectant in a bid to halt the spread of the Ebola virus.
Health workers and the hospital in Nzerekore were attacked by people reportedly shouting: "Ebola is a lie".
The exact cause of the riot is not clear - some also reportedly feared the spray would spread Ebola.
Meanwhile, Senegal has confirmed its first case of Ebola - a Guinean national.
The current outbreak of Ebola began in Guinea, and has killed more than 1,500 people in four countries.
There have been relatively few cases in Guinea recently, with far higher infection rates in neighbouring Liberia and Sierra Leone, and six deaths in Nigeria.
The World Health Organization (WHO) on Thursday warned that it could get much worse and infect more than 20,000 people.
Ebola Virus Disease (EVD)
- Symptoms include high fever, bleeding and central nervous system damage
- Spread by body fluids, such as blood and saliva
- Fatality rate can reach 90% - but current outbreak has mortality rate of about 55%
- Incubation period is two to 21 days
- There is no vaccine or cure
- Supportive care such as rehydrating patients who have diarrhoea and vomiting can help recovery
- Fruit bats, a delicacy for some West Africans, are considered to be virus's natural host
Journalist Guilana Fidel Monou told the BBC French service from Nzerekore that many people there still do not believe that Ebola exists.
He said that a market was sprayed following a funeral - although the death was not the result of Ebola.
Local traders were apparently not warned and held a protest march to the city's hospital, which was attacked.
Police responded by firing tear gas and a 24-hour curfew was imposed.
Local Red Cross workers had to flee to a military base, reports the Reuters news agency.
Youssouf Traore, president of the Guinean Red Cross, said the rioters had fired guns.
"A rumour, which was totally false, spread that we had sprayed the market in order to transmit the virus to locals," Mr Traore said.
This is not the first time that health workers trying to combat Ebola have been attacked.
Nzerekore is the capital of the Forest Region, where the Ebola epidemic has its epicentre, however the BBC's Alhassan Sillah in Guinea says the town has miraculously remained free of Ebola so far.
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