The Saudi Arabia affiliate of Islamic State of Iraq and Syria (ISIS) has claimed responsibility for the deadly suicide bombing attack on a Shiite mosque on Friday that killed at least 21 people and injured more than 100 others. 

Islamic State said in a propaganda statement that "the soldiers of the Caliphate" were behind the attack carried out by a suicide bomber who "detonated an explosives belt" in a mosque, Al Jazeera reported. It is first time ISIS claimed responsibility for an attack on Saudi Arabia.

The Associated Press reported that the Islamic State also warned Saudi Arabia- a Sunni Kingdom- of more "black days" ahead. The militant group also vowed to expel all Shiites from the Arabian Peninsula.

The attack took place at the Imam Ali mosque located in Al-Qadeeh village of eastern Qatif province. An Islamic State bomber, identified as Abu Amer al-Najdi , blew himself up when the mosque was filled with worshippers for weekly midday prayers, according to The Wall Street Journal.

"Security authorities will spare no effort in the pursuit of all those involved in this terrorist crime," the Interior Ministry spokesman said, leading Saudi newspaper Asharq Al-Awsat reported. Saudi Arabia will "hunt down anyone involved in this terrorist crime carried out by people seeking to undermine national unity," spokesperson added, according to AFP.

This is the second terrorist attack to target Saudi Arabia's Shi'ite community in the past six months. Eight people were shot dead when gunmen attacked a Shi'ite mosque in Al-Ahsa in November, Asharq Al-Awsat reported. Islamic State leader Abu Bakr al-Baghdadi called for jihad in Saudi Arabia in a video speech released in November 2014.

The U.S. condemned the attack, but, was unclear about ISIS's claim of responsibility.

"We obviously mourn the loss of life and condemn this violence," White House spokesperson Josh Earnest said, according to Voice of America. "The attribution, the determination about who is responsible, is still under review."