A victim receives treatment at a hospital following twin blasts at a Kabul wrestling club on September 5, 2018. (Photo: VCG)

At least 20 people have been killed, including two Afghan journalists, after twin blasts at a Kabul wrestling club on Wednesday that left another 70 wounded in the latest assault on the capital.

An hour after a suicide bomber blew himself up inside the sports hall in a heavily Shiite neighborhood, a car packed with explosives detonated as journalists and security forces gathered at the scene, a police spokesman said.

At least four journalists were wounded in the second explosion, media support group NAI said.

Tolo News, Afghanistan's largest private broadcaster, confirmed two of their journalists were killed.

There was no immediate claim of responsibility for the twin explosions. The Taliban denied involvement.

"An attack on civilians and media workers of the country is an attack on freedom of speech and crime against humanity," Afghan President Ashraf Ghani said in a statement condemning the latest violence.

Civilians paying the price

Civilians have long borne the brunt of the violence in Afghanistan – especially in Kabul, a target of both the Taliban and IS.

Journalists also have paid a heavy price covering the conflict. At least 11 were killed in the first six months of the year, the Afghan Journalists Safety Committee said in a report.

Wednesday's attack comes a day after the Taliban announced the death of Jalaluddin Haqqani, who founded the eponymous militant group which is widely suspected of being behind some of the attacks in Kabul claimed by IS.