An ISIS affiliate in Afghanistan has claimed responsibility for an attack that is underway in Kabul.

:: Gunmen stormed a Shiite mosque in the Afghan capital while worshippers were at Friday prayers, setting off an explosion that killed a security guard outside and pushing into the two-story building, officials said. A cleric who was leading the service was also killed, according to reports.

An ISIS affiliate in Afghanistan has claimed responsibility for an attack that is underway in Kabul.

ISIS’ Aamaq news agency carried the claim on its website on Friday. In the claim, ISIS says two of its fighters, seeking martyrdom, carried out the assault. It did not give further details.

Meanwhile, the death toll from the suicide bomb and gun attack claimed by the ISIS group on a Shiite mosque in Kabul Friday has risen to 20, an Afghan official said.

“We have 20 killed and more than 50 wounded,” Mohammad Ismail Kawoosi, a health ministry official, told AFP.

The attack is the latest by ISIS to hit the Afghan capital. Last month, the group attacked the Iraqi Embassy in Kabul and afterward, issued a warning to all Shiites in Afghanistan, saying ISIS militants would attack Shiite places of worship.

Within days of the embassy attack in Kabul, ISIS also took responsibility for a brutal suicide assault on a Shiite mosque in western Herat province that killed 32 people.

On Friday police were promptly deployed at the site in a northern Kabul neighborhood and encircled the mosque. Initially they avoided advancing inside to prevent further casualties, police official Mohammed Jamil said.

Later, policemen made an attempt to enter the mosque but withdrew after one of the attackers set off an explosion, said police official, Mohammad Sadiq Muradi.

Mohammad Ismail Kawasi, a spokesman for Afghanistan’s health ministry, said authorities believe that along with the two dead so far, eight people were also wounded.

More explosions and gunfire echoed from the site of the attack, which Jamil said was still underway, well into the afternoon. The mosque had been packed with worshippers for Friday prayers, the high point of the Muslim week, Jamil added.

Mir Hussain Nasiri, a member of Afghanistan’s Shiite clerical council, said the cleric who was performing the prayers was killed, but did not give his name. Nasiri said the gunmen have taken over the portion of the mosque with the separate prayer areas for men and women.

He said the mosque could accommodate up to 1,000 people. A sprawling cavernous prayer hall dominated the main floor. The second floor is where the women pray. Nasiri said when police initially sought to get into the mosque, the attackers blocked the door leading to the second floor, which he said would mean they are holding the women who were there as hostages.

Witnesses in the area said sporadic shooting inside the mosque was continuing. They spoke on condition of anonymity, fearing for their safety.

There have been several attacks against Shiite Muslim mosques in Afghanistan in recent weeks. Last month, 32 people were killed when gunmen stormed a Shiite mosque in western Herat province. ISIS claimed responsibility for that attack and vowed to carry out more attacks against Afghanistan’s minority Shiite Muslims, which the Sunni extremists consider to be heretics.

Meanwhile, in southern Kandahar province, Afghan security forces repulsed a Taliban attack on an outpost, according to provincial police chief’s spokesman, Zia Durrani. Four members of the security forces died in the exchange and another seven were wounded, he said.

Durrani said the attack occurred overnight and the Taliban sustained heavy casualties. There was no immediate comment from the Taliban.

Elsewhere, provincial deputy police chief Nisar Ahmad Abdul Rahimzai saids that Afghan security forces recaptured a district in eastern Paktia province from the insurgents.

The summer fighting season in Afghanistan has been brutal so far this year, with relentless Taliban attacks around the country as the insurgents battle to expand their footprint.

Afghan policemen take position after an attack on a mosque in Kabul.

An Afghan worshipper is consoled as he cries near the site of suicide attack that targeted a mosque in Kabul on Friday.