The South African National Defence Force (SANDF) are to be on the streets for at least three months to boost the city's struggling police force under the order authorised by President Cyril Ramaphosa.

The number of soldiers deployed was not revealed.

Ramaphosa told lawmakers the soldiers would support police "to restore law and maintain order in communities that are being terrorised by gangsterism and tackle "the most extreme incidents of violent crime".

Troops in full combat gear brandishing assault rifles were seen standing beside military personnel carriers at road junctions in the Manenberg township in eastern Cape Town.

The army has been used in similar missions in Cape Town before. It was called out this time to respond to a spike in violence in recent months in the sprawling townships of the Cape Flats area, one of the most dangerous places in South Africa.

Cape Town, an international tourist destination with stunning coastal and mountain scenery, has the highest murder rate in the country, according to the latest official crime figures.

Police minister Bheki Cele said murders in the Western Cape province, which includes Cape Town, increased 6.3 percent from 3,729 to 3,963 during the year to April 2019.

Last year, over 20,000 people were murdered in South Africa -- 57 per day -- and Cele has described the country as "close to the war zone".

Many wealthy people live in fortified homes with high walls topped with electrical wires, CCTV monitoring and armed guards.