KINSHASA - Eight more cases of the deadly Ebola haemorrhagic fever have been confirmed in the Democratic Republic of Congo, bringing the total to 17, a World Health Organisation official in Congo said on Tuesday.

Health workers were rushing to erect two mobile laboratories, for speedier diagnosis of cases, at two villages in southern Kasai Occidental province, where the outbreak of the highly contagious disease was confirmed earlier this month.

Previous test samples have been sent overseas, mostly to the United States. The on-site mobile labs being installed were lent by the United States and Canada.

"We sent the second batch of 42 samples to the Centers for Disease Control and Prevention (CDC) in Atlanta. Eight tested positive for Ebola. So we now have 17 (cases) total," WHO spokesperson Christiana Salvi told Reuters by phone from Luebo, one of the villages at the epicenter of the outbreak.

Six of the 17 known Ebola victims have died but the number of Ebola deaths could rise as further laboratory test results were expected from the CDC.

Ebola, which causes death in 50 to 90 percent of cases, is transmitted by contact with the blood, secretions, organs or other bodily fluids of infected persons.

Symptoms begin with fever and muscle pain, followed by vomiting, diarrhoea and in some cases bleeding from orifices.

Typhoid and Shigella dysentery have also been confirmed in Kasai Occidental, where authorities have reported 170 deaths among 400 sick people in the past five months.

The WHO's Salvi said rapid diagnosis provided by the on-site mobile laboratories would help doctors on the ground to quickly isolate and begin treatment of confirmed cases.

"They could be operating by tomorrow," she said. "It will take them from two to six hours then to have a diagnosis. That will speed things up a great deal."

In Geneva, WHO spokeswoman Fadela Chaib said the number of people admitted to health centres and hospitals during the outbreak was slowly declining.

International experts were examining hospital records and contacting family members in their investigation into the multiple outbreaks, she said.

"It will take time to be able to understand retroactively what happened and what caused disease and death," Chaib said.

The WHO and Belgian chapter of the medical relief agency Medecins Sans Frontieres (MSF) have already sent tonnes of supplies to the areas affected by the outbreak.

They have also dispatched teams of doctors, nurses, epidemiologists and Ebola experts.

Messages were being aired on the radio and television to warn people how to avoid transmission of Ebola, which can occur at burial ceremonies where mourners have direct contact with corpses.

Western Kasai is east of Kikwit, the site of a major Ebola outbreak in the former Zaire in 1995, which killed 250 among 315 people infected.