The death toll rose quickly, reaching more than 100 by the time this page went to press. The world, horrified again, watched as details of the most recent madness emerged in Paris just 10 months after attacks by Islamic extremists at a newspaper office and a kosher grocery.

In multiple attacks Friday, explosions were heard outside a soccer stadium; people were shot and killed in a restaurant, and dozens died in a concert hall in which hostages were taken and an American band reportedly was playing. News reports described a city under siege, and French President Francois Hollande announced that he was closing the country’s borders, mobilizing the military and declaring a state of emergency.

“As I speak, terrorist attacks of an unprecedented scale are taking place in the Paris region,” Hollande said in a televised address. “There are several dozen dead, lots more wounded, it’s horrific.”

It’s not as if Paris let down its guard after the January attacks on the grocery and the offices of the satirical newspaper Charlie Hebdo. France has been on alert, with officials warning of a heightened terror threat. In fact, tighter security measures already were in place in advance of a global climate conference that starts in two weeks.

As of late Friday, officials had not yet publicly identified the group or groups believed to be responsible for the newest round of attacks, but for obvious reasons speculation immediately turned to Islamic militants, more specifically the Islamic State in Iraq and the Levant (ISIL).

Officials in France, the U.S. and other countries have been especially concerned about the potential for violence from Islamic radicals who have returned or have attempted to return to their home countries after traveling to Syria. If ISIL is indeed responsible, the attacks are further deadly proof of the need for a global response to the growing threat posed by the group.

Unless officials decide to delay the talks, the attacks are likely to be Topic A at the G-20 summit scheduled to begin Sunday in Turkey. The summit provides a perfect opportunity for the world’s most powerful countries to present a united front in the aftermath of Friday’s nightmare in Paris.