ISIL claims Shia mosque suicide attack in Saudi Arabia

A suicide bomber struck a mosque in eastern Saudi Arabia as worshippers were commemorating the 7th century birth of a revered Shia figure, killing at least 21 people on Friday, the first attack in the Kingdom to be claimed by ISIL.

Saudi Arabia's Interior Ministry reported that an explosion struck a mosque in the eastern province of Qatif after Friday prayers. More than 150 people were praying when the huge explosion ripped through the Imam Ali mosque in the village of al-Qadeeh, witnesses said.

The Islamic State in Iraq and the Levant (ISIL) said in a statement that one of its suicide bombers, identified as Abu 'Ammar al-Najdi, carried out the attack using an explosives-laden belt, U.S.-based monitoring group SITE said on its Twitter account. ISIL said it would not rest until Shias, which the group views as heretics, were driven from the Arabian peninsula.

It is the second deadly attack in six months against minority Shia, who make up as much as 20 percent of the Kingdom's population. In November, ISIL was blamed for shooting dead eight worshippers in eastern Saudi Arabia's al-Ahsa village.

Activist Naseema al-Sada told The Associated Press by telephone from Qatif that the suicide bomber attacked worshippers as they were commemorating the birth of Imam Hussain, a revered figure among Shia. She said the hospital has called on residents to donate blood.

A witness to the attack told the AP that the attacker detonated his suicide vest just as he was entering the mosque. The witness spoke on condition of anonymity for fear of retribution.

Lebanon's Al-Manar television channel, run by the Lebanese Shia Hezbollah group, carried still, blurry pictures of pools of blood inside what appeared to be the mosque where the attack took place. It also showed still photos of at least three bodies stretched out on red carpets, covered with sheets. One person dressed in a white robe was being carried away on a stretcher.

Shia residents in eastern Saudi Arabia have long complained of discrimination. They say that despite the region being home to most of the kingdom's oil reserves, their streets, buildings and infrastructure are in poor condition. They say unemployment runs high among Shia youth in the area.

In 2011, Shia in the east inspired by the Arab Spring uprising in neighboring Bahrain took the streets to demand greater rights. Police arrested hundreds of people and a Saudi court sentenced an outspoken cleric, Nimr al-Nimr, to death.

Al-Sada and others say that Saudi Arabia's airstrikes against Shia rebels in Yemen have further inflamed sectarian tensions. Since the Saudi-led war began in late March, many leading Sunni clerics in the kingdom have used Friday sermons to denounce the Houthi rebels and their Iranian backers, but also to criticize their practices of praying at tombs and shrines.

Many Sunni Wahhabi Muslims in Saudi Arabia view the Shia practice of praying at the tombs of religious figures as akin to polytheism.

"I hold the government responsible," al-Sada said. "The government should protect us, not encourage sermons and schoolbooks to incite against us as non-believers."

"We want them to prevent this from happening in the first place," she said.

Just before the Saudi-led campaign against the Houthis, suicide bombers in Yemen's capital attacked a pair of mosques, killing 137 people. A purported affiliate of the Islamic State group claimed responsibility for the bombings, which also wounded 357 people.

Al Jazeera and wire services