Internal conflict is hampering efforts to rein in an Ebola outbreak in the Democratic Republic of Congo, the WHO has warned, urging a ceasefire to stop the virus from spreading.

The death toll from the latest outbreak rose to 41 people by August 1 in DRC's North Kivu province.

Tedros Adhanom Ghebreyesus, the World Health Organization chief, has called for the rapid roll-out of an unlicensed drug being used for the first time to treat Ebola patients.

Ghebreyesus told reporters on Tuesday he feared conditions on the ground in the eastern province had created "a conducive environment for the transmission of Ebola".

The outbreak in North Kivu's Beni region, which shares borders with Uganda and Rwanda, was declared a week after WHO and the Kinshasa government hailed the end of an Ebola flareup in northwestern Equateur province, which killed 33 people.

The latest outbreak, which now counts 57 probable and confirmed cases, is the country's 10th since 1976, when the disease was first identified in the DRC near the Ebola River.

DRC health authorities said Tuesday that for the first time since the outbreak was announced, one fatality was recorded outside of North Kivu - in the neighbouring province of Ituri.

The new outbreak poses the same problems as past cases in the DRC, including logistical hurdles in a country with weak health infrastructure.

But in North Kivu, health workers are being forced to navigate their response among more than 100 armed groups.

Ghebreyesus said that there have been 120 violent incidents since January.

He said the region was sprinkled with so-called "red zones", or inaccessible areas.

"That environment is really conducive for Ebola ... to transmit freely.

"We call on the warring parties for cessation of hostilities, because the virus is dangerous to all. It doesn't choose between this group or that group," he said.

Ebola causes serious illness including vomiting, diarrhoea and in some cases internal and external bleeding. It is often fatal if untreated.

In a bid to halt the virus' advance, DRC health authorities said Tuesday that doctors in Beni had begun using a prototype drug called mAb114 to treat patients.

Developed in the US, the prototype drug is a protein that binds on to a specific target of the virus and triggers the body's immune system.

In May, the US National Institute of Allergy and Infectious Diseases (NIAID) said it was carrying out the first human trials of mAb114 to test it for safety and tolerance.

Ghebreyesus said five patients had received the unlicensed drug so far, and that WHO would like the roll-out "to speed up as much as possible".

Targeted vaccination, aimed primarily at frontline health workers, began last week, and so far 216 people have received a jab.