International health officials are investigating the emergence of a mysterious disease in Angola that has killed at least four people and sickened more than 200.

The illness, which leads to weakness, muscular spasms, mental confusion and speech impairment, surfaced in Cacuaco, near Luanda, in early October, the World Health Organization (WHO) said in a press release sent to Reuters late on Tuesday.

It has since spread to seven neighbourhoods in the municipality, about 20 km (12.5 miles) north of the Angolan capital and home to some 200,000 people.

"As of 1st of November, more than 200 cases including four deaths have been reported," the WHO said in its statement.

Experts from the WHO, U.S. Centers for Disease Control and Prevention (CDC) and the Angolan government are investigating the outbreak.

"The Ministry of Health advised the population to observe the individual and collective measures, especially food hygiene, to avoid all risk factors related to solid wastes and to go to the nearest health facilities if suffering from any signs of sickness," the WHO added.

Angola suffered an extensive cholera outbreak last year that killed at least 1,800 people. Some 150 Angolans died in 2004-2005 after contracting Marburg virus, a close relative of the feared Ebola virus.

The oil-rich southwestern African nation is struggling to rebuild its health system, which was devastated during a 27-year civil war that ended in 2002. Millions were left vulnerable to malnutrition and other diseases due to the conflict.

An estimated one-quarter of babies and toddlers die before the age of 5.

Although former colonial power Portugal established a rudimentary health system while ruling Angola, services crumbled after independence in 1975.