ISLAMABAD (AP) — An affiliate of the Islamic State group claimed responsibility overnight for a deadly suicide bombing inside a Shiite mosque on the outskirts of Pakistan’s capital that killed 31 people and wounded 169 others, as mourners gathered Saturday under tight security at the same mosque for funerals for the victims.

The regional Islamic State affiliate, known as Islamic State in Pakistan, claimed responsibility in a statement posted on its Amaq News Agency. It said the attacker arrived opened fire on security guards who tried to stop him at the main gate and detonated his explosive vest after reaching the mosque’s inner gate.

The Islamic State group suggested it viewed the Pakistani Shiites as legitimate targets, calling them a “human reservoir” that provided recruits to Shiite militias fighting the Islamic State in Syria.

Friday’s mosque bombing was the deadliest in Islamabad since a 2008 suicide bombing at the Marriott Hotel that killed 63 people and wounded more than 250. In November, a suicide bomber struck outside a court in the capital, killing 12 people.

The latest attack comes as Prime Minister Shehbaz Sharif’s government has had to deal with a surge in militant attacks across Pakistan. According to Pakistani authorities, the attacker was a Pakistani national who had recently traveled to Afghanistan.

Authorities said several suspects, including the brother, mother and other relatives of the bomber, were arrested during overnight raids in Islamabad and in northwestern Pakistan, and that a police officer was killed in the operation.

More than 2,000 grief-stricken mourners gathered as coffins of those killed were brought to the mosque for funerals. Senior government officials and leaders of the Shiite community were among those who attended the funerals for about a dozen victims. Funerals of other victims were to be held in their home towns.

IS is a Sunni group that has targeted Pakistan's Shiite minority in the past, apparently seeking to stoke sectarian divisions in the majority Sunni country. In 2022 it claimed responsibility for a suicide bombing that struck a Shiite Muslim mosque in Pakistan’s northwestern city of Peshawar, killing at least 56 and wounding 194.

Pakistan's Defense Minister Khawaja Mohammad Asif told reporters Friday that the attack signaled that Pakistan-based militants operating from Afghanistan could strike even in the capital.

His remarks drew a sharp response from Afghanistan’s Taliban government.

In a statement, Afghanistan’s Defense Ministry condemned the mosque attack in Islamabad but said the Pakistani defense minister had “irresponsibly” linked it to Afghanistan. Pakistan has frequently accused Afghanistan, where the Taliban returned to power in August 2021, of harboring militants, including members of the Pakistani Taliban. Kabul denies the accusations.

The attack also drew condemnation from the international community, including the United States, Russia and the European Union.

Prime Minister Sharif said he was grateful for the messages of sympathy and support received “from across the globe” following what he called a “heart-wrenching suicide attack in Islamabad.” He said international support remained critical to Pakistan’s counterterrorism efforts and vowed the perpetrators would be brought to justice.

Although Pakistan's capital has seen relatively few attacks compared with other regions, the country has experienced a recent rise in militant violence. Much of it has been blamed on Balochseparatists and the Pakistani Taliban, known as Tehrik-e-Taliban Pakistan, or TTP, which is a separate group but allied with Afghanistan’s Taliban.

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Associated Press writers Samy Magdy in Cairo, Riaz Khan and Rasool Dawar in Peshawar, Pakistan, and Ishtiaq Mahsud in Dera Ismail Khan, Pakistan, contributed to this story.