The Islamic State group claimed responsibility Tuesday for a suicide bombing Monday near Baghdad that targeted the funeral of a father whose sons fight in a Sunni militia sympathetic to the Iraqi government, the Associated Press reported. The Islamic State, formerly known as ISIS, admitted to the attack through a Twitter account it is known to use frequently.

While ISIS, a Sunni extremist group, usually attacks Shiite targets, the father’s funeral was targeted because the militia his sons are in is aligned with Baghdad’s Shiite-led government. The suicide bombing at a funeral tent north of Baghdad killed 16 people and wounded 34 others, according to the AP. Witness Hussein Ali told the news wire service that the suicide bomber disguised himself as a Shiite by wearing a religious flag and holding a picture of a Shiite imam.

The funeral tent was also serving food to pilgrims who were on their way to Samarra to commemorate the death in 874 of Hassan al-Askari, one of the 12 imams revered by Shiite Islam, according to Agence France-Presse.

“We were distributing food, fruit and tea to the pilgrims who were walking to Samarra, and a suicide [bomber] blew himself up,” a witness who only identified himself by his first name, Sajjad, told AFP.

Also on Monday, a retired Iraqi general who joined a Shiite militia, the Badr Brigades, was killed by a sniper in Duluiyah, about 45 miles north of Baghdad. In a statement posted to Facebook on Tuesday, Prime Minister Haider al-Abadi said retired Maj. Gen. Abbas Hassan Jaber “answered the call of the nation” and called him a martyr.

The Islamic State has seized large swaths of territory in Iraq and Syria and has carved out a self-declared caliphate where it imposes Sharia law.