BEIJING, China: Chinese President Xi Jinping on Monday sent a message of condolences to Pakistani President Asif Ali Zardari over last week’s deadly explosion in Islamabad.

On Friday an attacker opened fire at the gates of a Shiite Muslim mosque in Islamabad before setting off a suicide bomb and killing at least 31 people in the deadliest attack of its kind in Pakistan’s capital in more than a decade.

Xi “strongly condemned the violence and terrorist acts against innocent civilians,” and said China would support Pakistan in fighting terrorism, according to the state-run Xinhua news agency.

The Daesh group claimed responsibility for the attack in a statement on the Telegram messaging app.

Minister of Interior Moshin Naqvi told a press conference last week four people, including the alleged mastermind of the attack, had been arrested following an operation in Peshawar and Nowshera. During the operation one counter-terrorism officer was killed and three more were wounded, he said.

While bombings are rare in heavily guarded Islamabad, this is the second such attack in three months and — given a recent rise in militancy — they have triggered fears of a return to violence in Pakistan’s major urban centers.