Powerful Saudi Crown Prince Mohammed bin Salman condemned the attack on an Egyptian mosque that killed more than 300 worshippers and said it would galvanize an Islamic military coalition he convened in Riyadh on Sunday.
Top defense officials from some 40 Muslim-majority countries met for a summit aimed at countering "terrorism."
The alliance was announced two years ago by Prince Mohammed, who also serves as defense minister of the country which claims the mantle of leadership in the Islamic world.
This year he has pledged to restore the ultra-conservative kingdom to a more moderate and tolerant version of Islam.
"[The attack] was a very painful occurrence and must make us contemplate in an international and powerful way the role of this terrorism and extremism," Prince Mohammed said.
Gunmen attacked a mosque on Friday in Egypt's North Sinai killing more than 300 worshippers, including two dozen children.
The coalition has yet to take decisive actions but officials have described it as a grouping that would allow member states to request or offer assistance among themselves in fighting groups they designate as terrorists.
Such assistance could include military force, financial aid, materiel or security expertise, and will have a permanent base in the Saudi capital. The coalition will focus not only on a military, security and intelligence track but also efforts to combat terrorist financing and ideology.
"The biggest threat from terrorism and extremism is not only killing innocent people and spreading hate, but tarnishing the reputation of our religion and distorting our belief," Prince Mohammed said in opening remarks.
Iraq and Syria, which have been fighting Islamic State for the past three years, are not part of the coalition. Neither is Saudi arch-rival Iran, which Riyadh accuses of supporting terrorism.
Qatar, which has been isolated by Saudi Arabia and Arab allies for the past six months over alleged support of terrorism, was originally part of the coalition but did not appear to be in attendance at Sunday's meeting.
Want to enjoy 'Zen' reading - with no ads and just the article? Subscribe todaySubscribe now