Flames could be seen and a column of smoke rose into the sky early on Sunday morning, beginning at about 5.30am local time (3.30am in the UK).

The blaze started in third-floor offices and spread to the National Assembly chamber, local fire service spokesman Jermaine Carelse said, adding that no one had been injured.

The roof area also caught light and authorities feared that parts of buildings, some of them first built in the late 1800s, might collapse because of the heat.

Some 35 firefighters are on the scene tackling the blaze.

Patricia de Lille, minister of public works, said the flames had been contained in the chamber of the National Council of Provinces - the upper house - but continued to burn in the National Assembly chamber.

"We can't tell you exactly where the fire started," she said, adding that it was a "very sad day for our democracy".

Police have begun to investigate and President Cyril Ramaphosa has been briefed.

The president and many of South Africa's high-ranking politicians were in Cape Town for the funeral service of Archbishop Desmond Tutu, which took place on Saturday at the city's St George's Cathedral, about a block away from the parliament precinct.