KANDAHAR (AFP) - The Islamic State of Iraq and Syria (ISIS) group on Saturday (Oct 16) claimed responsibility for a suicide bomb attack on a Shi'ite mosque in the southern Afghan city of Kandahar that killed at least 41 people and injured scores more.

The Friday assault came just a week after another ISIS-claimed attack on Shi'ite worshippers at a mosque in the northern city of Kunduz that killed more than 60 people.

In a statement released on its Telegram channels, the terror group said two Islamic State-Khorasan (IS-K) suicide bombers carried out separate attacks on different parts of the mosque in Kandahar - the spiritual heartland of the Taliban - while worshippers prayed inside. Khorasan is an old name for the region.

"The first suicide bomber detonated his explosive vest... in a mosque hallway, while the second suicide bomber detonated his explosive vest in the mosque's centre," the statement said.

The group, a bitter rival of the Taliban, a fellow Sunni Islamist movement, which swept back to power in Afghanistan in August as the United States and its allies withdrew, regards Shi'ite Muslims as heretics.

British-based conflict analysis firm ExTrac said Friday's assault was the first by IS-K in Kandahar, and the fourth mass casualty massacre since the Taliban took Kabul.

ExTrac researcher Abdul Sayed told AFP the attack was "challenging the Taliban claims of holding control on the country".

"If the Taliban can't protect Kandahar from an IS-K attack, how could it protect the rest of the country?" he asked.

Inside the mosque, after the blast, the walls were pockmarked with shrapnel and volunteers swept up debris in the ornately painted prayer hall. Rubble lay in an entrance corridor.

The Shiite minority group on Saturday buried their dead for the second Saturday in a row.

The killings triggered international condemnation. UN Secretary General Antonio Guterres condemned the "despicable attack" and demanded those using violence to restrict Afghans' religious freedom be brought to justice.

At the graveside, mourner Gul Ahmad told AFP of his grief over his brother's slaying: "He had two little children. He had a home to live in. He had everything. The pain of the loss cannot be described with words."

The all-male crowd brought body after body, shrouded in white sheets, as a dust storm was whipped up by the constant digging.

"The world will remember this. The Islamic world will remember this barbarism, specifically the dignified people of Afghanistan," warned another mourner, Muhammad Agha.

In the wake of the explosions, Kandahar police chief Maulvi Mehmood said "a brutal attack has been witnessed on a Shi'ite mosque as a result of which a huge number of our countrymen have lost their lives".

In a video statement, Mr Mehmood said security for the mosque had been provided by guards from the Shi'ite community but that henceforth, the Taliban would take charge of its protection.

Dr Hafiz Abdulhai Abbas, director of health for Kandahar, told AFP that 41 people had been killed and about 70 wounded, according to hospital information.

At least 15 ambulances were seen rushing to and from the scene as Taliban security cordoned off the area.

"We are overwhelmed," a doctor at the city's central Mirwais hospital told AFP.

"There are too many dead bodies and wounded people brought to our hospital. We are expecting more to come. We are in urgent need of blood. We have asked all the local media in Kandahar to ask people to come and donate blood."

Eyewitnesses spoke of gunfire alongside the explosions, and a security guard assigned to protect the mosque said three of his comrades had been shot as the bombers fought their way in.

Mr Sayed Rohullah told AFP: "It was the Friday prayer time and when we were preparing, I heard shots. Two people had entered the mosque. They had opened fire on the guards and in response, the guards had also opened fire on them. One of them committed a suicide blast inside the mosque."

Other bombs were detonated in crowded areas outside the main building, he and other witnesses said.

"We are saddened to learn that an explosion took place in a mosque of the Shi'ite brotherhood in the first district of Kandahar city, in which a number of our compatriots were martyred and wounded," tweeted Taliban Interior Ministry spokesman Qari Sayed Khosti.

US State Department spokesman Ned Price said Washington condemned the attack and reiterated a call for the "Taliban to live up to the commitment it has made to counter-terrorism, and specifically to taking on the shared threat we face from IS-K".

"We are determined to see to it that no group... can ever again use Afghan soil as a launching pad for attacks on the United States or other countries," he said.

The United Nations mission in Afghanistan in a tweet also condemned the "latest atrocity targeting a religious institution and worshippers".

"Those responsible need to be held to account."

The Taliban, which seized control of Afghanistan after overthrowing the US-backed government, has its own history of persecuting Shi'ites.

But the new Taliban-led administration has vowed to stabilise the country and, in the wake of the Kunduz attack, promised to protect the Shi'ite minority now living under its rule.

Shi'ites are estimated to make up roughly 10 per cent of the Afghan population. Many of them are Hazara, an ethnic group that has been persecuted in Afghanistan for decades.

In October 2017, an ISIS suicide attacker struck a Shi'ite mosque in the west of Kabul, killing 56 people and wounding 55.