More than 400 health workers at the only Ebola treatment center in southern Sierra Leone went on strike on Wednesday over unpaid risk allowances the government is meant to fund, officials said.

The clinic in Bandajuma in Bo district has about 60 beds for Ebola patients - about a fifth of Sierra Leone's total Ebola beds - and U.N. officials warn that the number of Ebola cases is surging in Sierra Leone due to a lack of treatment centers.

"An ambulance has just been turned away with a patient because the workers cannot go into the clinic if allowances are not paid," a representative of the striking workers, Mohamed Mbawah, said.

The basic salaries of staff at Bandajuma are paid by medical charity Medecins Sans Frontieres (MSF), which runs the clinic.

Mbawah said the government had not paid risk allowances since September and the strike would continue until workers had been fully reimbursed. It was not clear how many workers there are in total at the center.

The government was not immediately available for comment.

Ewald Stars, emergency coordinator for MSF, called on the government to pay the staff. "If the strike action continues we will shut down the treatment center," Stars said.

Sierra Leone is one of the three nations in West Africa worst affected by Ebola, which has killed nearly 5,000 people since it was identified in Guinea in March.

Liberia, the hardest hit by Ebola, has seen a reduction in the number of new cases. However, the U.N. Ebola response mission, UNMEER, warned last week that Sierra Leone has just 288 of the 1,864 beds it needs to fight the disease.