Several people have been killed in a bombing outside a mosque in the Afghan capital Kabul, reported BBC news. The Taliban’s interior ministry spokesperson was quoted saying that at least five civilians had died. 

The attack is the first major explosion in Kabul since the Taliban swept to power over a month ago. The BBC reports that the explosion injured up to 20 people who were at the Eid Gah Mosque, where a prayer ceremony was being held for the late mother of a Taliban spokesman.

So far, no group has claimed responsibility for the attack, but it is likely believed that IS militants are behind the bombing. Hours after the attack, Taliban forces launched their own attacks on suspected IS hideouts and unverified reports suggest three militants were killed. 

The attacks highlight the deep underlying tensions between the Islamic State Khorasan (the Afghan and Pakistani affiliated branch of the Islamic State) and the Taliban. Even when both groups were pitted against the previous Afghan government, they would regularly clash over resources, ideology and territory. 

The Taliban is under immense international pressure to prove that they can distance themselves from IS and al-Qaeda and to not allow Afghanistan to become a base for foreign terror organizations. So far, the Taliban has adamantly denied that either terror group operates on Afghan soil. This bombing attack will cast doubt on those claims. 

While the attack happened outside the mosque, it is unclear if it was directly targeting the prayer ceremony happening at the time. 

Al Jazeera News reported that the attack was the deadliest in the country since a suicide bomber attack targeted the U.S. evacuations from Kabul in August. That blast killed 169 Afghan civilians and 13 U.S. soldiers. The attack is a reminder that even though the Taliban may hold the seat of power, Afghanistan remains very much a contested country.