Police in Liberia's capital, Monrovia, have fired live rounds and tear gas during protests after a quarantine was imposed to contain the spread of the deadly Ebola virus.
Residents of the capital's West Point slum area say the barbed wire blockade stops them buying food and working. Four people are said to have been injured in the clashes.
Liberia has seen the most deaths - 576 - in the world's worst Ebola outbreak, which has hit West Africa this year. A total of 1,350 have died in four countries - Guinea, Nigeria and Sierra Leone, as well as Liberia.
Hundreds of West Point residents protested on Wednesday after security forces erected blockades around the slum. One 15-year-old boy was injured in West Point as he tried to cross the barbed-wire barricades erected by the security forces, who fired into the air to disperse the protesters.
"I don't have any food and we're scared," West Point resident Alpha Barry told Reuters news agency.
Residents of other Monrovia districts said they were unhappy at not being able to buy food in West Point market.
"We go to West Point market to buy food for our children, and since this morning our children have not yet eaten," Hawa Massally told AP.
The BBC's Jonathan Paye-Layleh in Monrovia says troops are patrolling in West Point, the country's largest slum which is home to more than 50,000 and sprawls along the Atlantic coast. Ferries have been halted and coast-guard boats are monitoring the coastline.
Our reporter says fear and tension has been growing in the slum for days and residents feel not enough has been done to protect them. But President Ellen Johnson Sirleaf said people were not heeding government warnings.
"We have been unable to control the spread due to continued denials, cultural varying practices, disregard for the advice of health workers and disrespect for the warnings by the government," she said on Tuesday evening.
Some people have dismissed the Ebola outbreak as a hoax, while others do not trust Western medicine, saying the disease is the result of witchcraft.
Dolo Town, about 40km (25 miles) from Monrovia, has also been put under quarantine and all entertainment centres are to be closed and video centres are to shut by 18:00 local time.
President Ellen Johnson Sirleaf also imposed a nationwide curfew. There is no known cure for Ebola, but the WHO has ruled that untested drugs can be used to treat patients in light of the scale of the current outbreak.
The experimental drug ZMapp has been used to treat several people who contracted Ebola in Liberia but the US firm that makes the drug says it has for now run out of it, so the only way to stop the current outbreak is to isolate the victims.