South Africa is reeling in shock from a spate of weekend shootings in which armed men burst into three bars and opened fire indiscriminately, killing 21 people.

Regional and ethnic rivalries, an organised extortion ring, competition between bar owners and political enmities are all possible motivations for the shootings, say analysts.

It is not known if the shootings are linked.

The worst was in Johannesburg’s Soweto township where 15 people were killed and several seriously injured when men charged into a bar and started shooting with semi-automatic rifles late on Saturday night, said police.

More than 135 cartridges were found at the scene, indicating the attackers were shooting to cause maximum casualties, police said.

A manhunt has been launched for five suspects in the Soweto shooting, police minister Bheki Cele said at a press conference on Monday at the bar in the Nomzamo area.

The suspects have been traced to Nongoma township in coastal KwaZulu-Natal province, he said.

In the city of Pietermaritzburg in KwaZulu-Natal, gunmen opened fire in a tavern in the Sweetwaters area late on Saturday night, killing four people, before speeding away in a small vehicle, said police. Two suspects have been arrested.

Two more people were killed at a tavern in Katlehong township, in the Ekurhuleni area south of Johannesburg, when two gunmen opened fire on patrons late on Friday night.

Security analyst Stephen Buchanan-Clarke said: “It is difficult to say definitively at this stage what the nature of these attacks is. It is quite telling though that in all three situations nothing was stolen. It seems the patrons targeted were done so to send a wider sort of message.

“So in that sense, it does resemble something similar to a political, organised terrorist attack than a purely criminal attack.

“We are not sure whether it is driven by a wider political agenda, perhaps trying to foment ethnic cleavages or stir up some political anger ahead of the ANC (ruling party) conference later this year.”

Crime researcher Ziyanda Stuurman said the method of the shootings indicated possible involvement of organised crime. It could be an extortion gang “trying to squeeze a protection fee out of the tavern owners,” she told South Africa’s News24 website.

Police have deployed a special tactical response unit known as amabherethe to Soweto’s Nomzamo area.

Amabherethe in township slang means berets, referring to the hats worn by the unit. The amabherethe forces, often criticised as heavy-handed, are patrolling the area, said Mr Cele.

“We ask the community to co-operate with them,” he added. “We want the police to take over these streets, so that it is us (police) running them, not these criminals.”

The Gauteng Liquor Forum, which represents tavern owners in the province, said it is concerned about an increasing number of violent attacks at South African taverns.

“While tavern owners have worked hard to improve security, they are simply no match for this level of indiscriminate and violent criminal behaviour. Tavern owners are following government laws and regulations, but it appears that they are being targeted,” the group’s chairman Fanny Mokoena said.

Soweto residents on Monday told Mr Cele there was a huge number of illegal firearms in the area and pleaded with police to tackle it.

Amnesty International South Africa condemned the killings and called for a thorough investigation by police.

“It is now up to the South Africa Police Service to conduct thorough, efficient and transparent investigations into the shootings that took place over the weekend and ensure that the perpetrators are charged in accordance with the law,” executive director Shenilla Mohamed said in a statement.

“We can no longer allow horrendous crimes in South Africa to continue with impunity.”