A popular South African radio and club DJ has been shot dead in the country's largest city, Johannesburg, sending shockwaves across the nation grappling with entrenched crime.

Warrick Stock, popularly known as DJ Warras, was gunned down in the city centre on Tuesday afternoon.

Police said the 40-year-old media personality was approached by three suspects, one of whom opened fire on him before fleeing on foot.

The motive of the shooting is unknown and no arrests have been made, police said.

Stock was a well-known radio and TV presenter and a podcaster in South Africa.

Fred Kekana, a local police chief, said Stock was attacked outside Zambesi House near Carlton Centre.

Stock spent several hours at the building overseeing the installation of security systems at the premises, which had been controversially occupied by unknown people, reports the state-run SABC.

"It is alleged the victim was approached by three unknown suspects after parking his vehicle, and they opened fire at him before fleeing the scene on foot," the South African Police Service (SAPS) said in a statement.

CCTV footage showed a man with dreadlocks and dressed in what looked like a security uniform opening fire on Stock before fleeing, said Kekana.

The DJ tried to run away after he was shot but fell down across the street, the police chief added.

He said that Stock had an unused firearm on him and nothing was taken during the attack.

Key evidence, like cartridges, were discovered at the scene, according to the police.

Police have appealed to eyewitnesses and members of the public who may have seen the suspects to come forward.

"We know they walked a long distance after the shooting, and officers have been tracking them to determine their whereabouts," added Kekana.

His sister Nicole Stock told SABC that the family was struggling to process his death.

"I am in shock. I don't have words. I am shattered," she said.

"We know he was a voice for many people around the country. He spoke out bravely about issues not many people were willing to speak about. This is a tremendous loss."

She appealed to the public to refrain from sharing graphic images or videos from the scene, saying this was an incredibly difficult time, especially for Shock's three sons.

Stock was the presenter of Ngicel' iVisa, a reality show that premiered on Mzansi Magic, a South African digital satellite entertainment channel.

Beyond his media career, Stock was involved in various business ventures, including private security, providing elite guarding and VIP protection services and securing high-profile events across South Africa, according to local media.

He was also reportedly involved in property management and assisted with building evictions.

His murder has shocked the country and prompted an outpouring of tributes from his fans, the government and political parties.

Sports, Arts and Culture Minister Gayton McKenzie said he was angry and saddened by Stock's murder.

"He spoke his truth without fear or favour. He even spoke up against me and my decisions as a minister. He was a pure example of who we should be," added McKenzie.

Leader of South African's Build One party Mmusi Maimane said the "brazen murder of DJ Warras in broad daylight is a shock for all South Africans".

"DJ Warras was more than just a face of a reality series. He was a talented storyteller, a passionate music lover and a warm soul who brought joy and energy to every moment on screen. His dedication to creativity left an indelible mark on our channels," said Shirley Adonisi, director of local entertainment Channels (Mnet).

In a statement, Mzansi Magic said Stock was known for his charisma, warmth and sharp wit, adding that his legacy "will live on".

South Africa, the continent's most industrialised nation, has one of the world's highest murder rates, fuelled by robberies and gang violence, with some 63 people killed each day between April and September, according to police data.