Twenty-seven people were killed in two separate mass shootings in South Africa within hours of each other, adding to the country’s long-running problem of gun violence.

Police investigate a mass shooting in South Africa as 27 people are killed in attacks near Johannesburg and Cape Town. (Photo by RAJESH JANTILAL / AFP) (AFP)

The first shooting happened near Johannesburg on Saturday evening. Eight gunmen reportedly stormed a bar and opened fire on people gathered outside the venue before continuing the attack inside, according to police.

Seventeen people were killed in the Johannesburg-area shooting, while another 15 people were injured. Police said the victims in the Johannesburg shooting included 13 men and four women, according to the BBC. The attackers also set two vehicles on fire before fleeing the scene, police said.

Police have not confirmed the motive for the Johannesburg attack. However, Deputy Provincial Police Commissioner Maj Gen Fred Kekana said the shooting may have been a retaliation linked to an earlier incident. The earlier incident happened last month, when one person was killed and another was wounded, Kekana said, according to AFP.

Police said they already had clear images of some of the suspects and, in some cases, knew their names, according to Kekana. The second shooting happened in the early hours of Sunday morning outside an entertainment venue in a township near Cape Town, according to the BBC.

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Ten people were killed in the Cape Town-area shooting, while another 11 people were injured. Five victims died at the scene, while another five later died in hospital. No arrests had been made in either shooting by Sunday morning.

The two attacks happened only days after another mass shooting in Durban, where 11 people were killed after gunmen stormed a house in the KwaMakhutha township, according to the BBC.

Recent mass shootings have raised concerns that the violence may be getting worse, particularly in areas affected by organised criminal activity. Gang turf wars are one major source of violence. These conflicts are often connected to criminal activities including drug trafficking and illegal mining, according to the BBC.

South African President Cyril Ramaphosa said in February that organised crime was “the most immediate threat” to the country’s democracy, society and economic development. The government has also taken steps to increase security in areas with high murder rates.

Earlier this year, the military was deployed alongside police in some of the country’s most violent areas in an effort to reduce armed violence.

Local police said they could not rule out the possibility of a serial killer operating in the area because of similarities between some of the deaths, according to the BBC. The two latest mass shootings therefore come amid a wider security crisis involving gang violence, illegal weapons, organised crime and a high murder rate in parts of South Africa.

Police had not announced a confirmed motive or arrests in either of the two latest mass shootings by Sunday morning, leaving investigators to determine who carried out the attacks and why.