Militant Sunni Muslims of the Islamic State bombarded a Shiite shrine north of Baghdad with mortar shells late Thursday night, as two suicide bombers in military uniforms blew themselves up inside, killing at least 35 people, according to Iraqi security forces.

The attack occurred just days after a particularly deadly Islamic State attack left nearly some 292 civilians dead in the Iraqi capital of Baghdad. Islamist militants drove an explosive-filled minibus into a Baghdad shopping district, blowing the vehicle up in one of the most lethal attacks to rock Iraq since the U.S. invasion in 2003.

Around midnight Thursday, the ISIS fighters bombed the mausoleum of Imam Sayyid Muhammad bin Ali al-Hadi, located in Balad, about 50 miles north of Baghdad. Al-Hadi is revered among Shiites, and numerous pilgrims had gathered there to celebrate the second day of Eid al-Fitr, which ends the holy season of Ramadan.

After the shelling, two suicide bombers infiltrated the complex and opened fire, before moving off to a nearby market where they blew themselves up, killing at least 35 and wounding another 60. A third suicide bomber was killed and his explosive belt defused, said a spokesman for the security forces, who attributed the attack to the Islamic State.

Early Friday the Islamic State jihadist group issued a statement claiming responsibility for the bombing, noting that a total of three militants loaded with explosives had died outside and inside the mausoleum of Sayyid Muhammad bin Ali al-Hadi.

Despite recent military setbacks in Iraq, the Sunni Islamic State group continues to commit bloody attacks, recently targeting the majority Shiite community, which they consider to be heretical.

The population of Balad where Thursday’s attack occurred is mostly Shiite, but the city is surrounded by many rural areas with Sunni majorities. Last month, at least 16 people were killed in Balad in Islamic State attacks striking a café and security forces.

Observers note mounting anger among Iraqis over the government’s inability to protect civilians and implement effective security measures.

In response to the attacks, the influential Shiite cleric Muqtada al-Sadr has ordered his militia to be deployed around the Balad mausoleum to try to ensure the safety of those present, as reported by Iraqi television channel Al Sumaria.

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