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, officials said, in the latest assault on the capital.

An hour after a suicide bomber blew himself up inside the sports hall in a Shia-majority neighbourhood, a car packed with explosives detonated as journalists and security forces gathered at the scene, police spokesman Hashmat Stanikzai 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, but the Islamic State group often targets Afghanistan's minority Shia community.

“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.

A spokesman at the interior ministry said at least 20 people were killed and another 70 wounded in the blasts. An Afghan security source confirmed the casualty toll.

Civilians and members of the security forces also were among the dead and wounded.

Health ministry spokesman Wahid Majroh had earlier put the death toll at 16 people and another 60 wounded.

“I was outside when the first explosion happened, which has killed over 30 people, many of them wrestlers,” Pahlawan Shir, director of the Maiwand wrestling club, told AFP.

“I was searching for my coach, I have finally found him in the... hospital. He is in a critical condition.”

Social media users who purportedly witnessed the attack said the bomber killed the guards at the club before blowing himself up inside.

He “detonated inside where a large number of athletes had gathered. There are a lot of dead and wounded”, Mohammad Hanif said on Facebook.

A photo posted on Twitter purportedly showed several victims being loaded into the back of a police pick-up.

Civilians paying the price

The last major attack on the Shia community in Kabul was on August 15 when a suicide bomber blew himself up in an education centre, killing dozens of students.

IS said it was behind that attack, which drew international condemnation and came amid a wave of deadly violence across the country.

Most of the victims were studying for college entrance exams when the blast happened.

That was followed a day later by an attack on an intelligence training centre in Kabul.

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. On April 30, twin explosions in Kabul killed nine journalists and 16 other people. Among the dead was AFP chief photographer Shah Marai.

AFP driver Mohammad Akhtar was killed less than three months later in a suicide attack in Kabul that also claimed the lives of 22 others.

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.

Afghan special forces arrested 11 Haqqani militants in Kabul and nearby districts, the country's intelligence agency said Wednesday.

The Taliban has been conducting blistering attacks on security forces across Afghanistan, including the massive, days-long onslaught on the eastern city of Ghazni last month.