Saudi Arabia confirmed Saturday the Islamic State group was behind the bombing of a Shiite mosque near Qatif in eastern Saudi Arabia that killed 21 people and injured 88 others. The Saudi Interior Ministry said a Saudi man carried out the suicide bombing at the direction of the militant group formerly known as either ISIL or ISIS, raising alarms it may be continuing to extend its reach beyond Iraq and Syria, the New York Times reported.

The bombing occurred after prayers Friday at the Imam Ali mosque in the village of al-Qadeeh. The attack was the first claimed by the Islamic State group inside the Saudi kingdom. It is believed to have been conducted in retaliation over the Saudi role in the Yemen conflict. Saudi Arabia has been conducting airstrikes against Houthi rebels and to stem Islamic State advances.

The ministry identified the suicide bomber as Salih bin Abdulrahman Salih al-Ghishaami, a Saudi citizen, who had been wanted by authorities for being a member of a terrorist cell, the Times said. However, the Islamic State group identified the bomber as Abu Amer al-Najdi.

The ministry said five other members of the cell had been arrested, charged in a drive-by shooting that targeted Riyadh police this month, the Wall Street Journal reported.

Al-Ghishaami had an explosives belt beneath his clothing when he entered the Imam Ali Mosque, authorities said.

Saudi Arabia's top Sunni cleric Saturday accused the Islamic State group of attempting to generate sectarian conflict in the kingdom, Reuters reported. "This totally criminal plot aims to split our ranks and sow chaos in our country, but, God be praised, it will not find a way. The nation and society are united and under a wise leadership," Grand Mufti Sheikh Abdulaziz Al al-Sheikh told state Al Ekhbariya TV.

Top local Shiite cleric Sheikh Mohammed Obeidan urged followers to remain calm. "We'll stand before anyone who thinks that our creed is a cause for fear or worry ... mass prayer -- in a calm, orderly way with self-restraint -- is the right way to respond to this corrupt force and hateful darkness," he told worshippers.

The Interior Ministry said earlier it was aware the Islamic State group planned sectarian attacks inside Saudi Arabia. Although Friday's attack was the first for which the militant group claimed responsibility inside Saudi territory, investigators have linked it to at least four other attacks since November.

Islamic State group leader Abu Bakr al-Baghdadi has urged followers in Saudi Arabia to "draw their swords" to kill Shiites, the Journal said.

Saudi Arabia's Shiite minority lives mainly in Eastern Province, where the attack took place. Members have accused the government of discrimination.