The Islamic State group Sunday posted an audio clip purporting to be of a suicide bomber who attacked a Shiite mosque in Kuwait’s capital on Friday, according to Reuters. The Najd Province, a branch of ISIS, took responsibility for the attack, which killed 27 people and injured over 200 at the mosque.

The posthumous statement reportedly consisted mostly of Koranic verses and was posted on social media channels used by ISIS. In the clip, the speaker slammed Shiite Muslims and threatened revenge for insulting Islam, Reuters reported. However, the authenticity of the statement could not immediately be verified, the report added. 

Shiite Muslims reportedly account for about a third of Kuwait’s population. ISIS, which is a Sunni group, regards Shiites as heretics, and a Twitter statement released by the militant group after the attack said that the bomber had targeted a “temple of apostates.”

The attack, which was carried out at the Imam Sadiq Mosque -- one of Kuwait's oldest Shiite mosques -- took place after Friday prayers during the holy month of Ramadan, when attendance typically increases at mosques. The bomber was identified as Fahad Suleiman Abdulmohsen al-Gabbaa, according to Kuwait's interior ministry. The attacker arrived on a flight to Kuwait International Airport at dawn Friday only hours before he detonated a bomb at the mosque, according to reports.

Kuwaiti officials have arrested the driver of the car that transported the bomber to the mosque. The driver was identified as Abdulrahman Sabah Eidan Saud. A Kuwaiti man who housed the driver was also taken into custody, and was reportedly described as a follower of a "fundamentalist and deviant ideology," according to the interior ministry.

Kuwait’s Islamic Affairs Minister Yacoub al-Sanna called the attack a “terrorist and cowardly action which threatens our nation and works at tearing apart the national unity,” according to the Associated Press, adding that the government will take all necessary measures to protect houses of worship in the country.

“Kuwait was and will remain the oasis of security and safety to all components of the Kuwaiti society and sects,” he reportedly said.