President Barack Obama said Sunday in a meeting with Turkish President Recep Tayyip Erdogan on the sidelines of the G-20 summit that the attacks in Paris were an “attack on the civilized world” and “the skies have been darkened” by the horrific assaulted.

Obama pledged U.S. solidarity with France in the effort to hunt down the perpetrators and bring them to justice. Erdogan, in turn, said there will be a “strong message” on fighting terrorism coming out of the summit.

Finding ways to stop Islamic State militants and the crisis in Syria , where the terror group has become entrenched, were already top priorities for world leaders at the G-20 summit in Turkey. But the series of coordinated attacks Friday night in and around the French capital in which at least 129 people were killed has created a heightened urgency to stop the Islamic State, which over roughly the past year has emerged as arguably the world’s deadliest and most dangerous terror group.

The group is also suspected of being involved in the downing of a Russian commercial jet Oct. 31 in Egypt's Sinai Peninsula, killing all 224 people on board. Intelligence experts suspect a bomb was planted in the aircraft.

Obama also said Sunday the U.S. stands with Turkey and Europe to reduce the flow of migrants. He said the U.S. and Turkey will redouble efforts to resolve Syria’s civil war.

Obama, whom Democrats and Republicans alike have urged to take a more aggressive approach toward eradicating the Islamic State in war-torn Syria, met Saturday with his National Security Council before departing for Turkey to discuss the latest intelligence regarding the attacks in Paris.

“This has to be an all-out effort,” New York Republican Rep. Peter King, a member of the House Permanent Select Committee on Intelligence, told ABC earlier this week. “I don't think the president has done enough as far as having the forces on the ground (in Syria) that are necessary to make the air attacks more effective.”

On Friday night, he tweeted that the Paris attacks were a “nightmare scenario.”

California Rep. Adam Schiff, the top Democrat on the chamber’s Intelligence committee, agreed with King on ABC, saying the president's approach has essentially created “a battlefield that is pretty static” and that “more is going to have to be done.”

Schiff also suggested that eradicating ISIS could take 15 to 20 years without ground support from such countries as Jordan and Turkey -- from where Islamic State warriors appear to be gaining passage from Syria into Europe.

On Friday night, he expressed his sympathies to the French people and called the attacks “an unspeakable tragedy.”

The two-day, G-20 summit site of Antalya, Turkey had already been under heavy security, with the seaside resort, just a few hundred miles from the Syrian border, essentially closed. And the adjacent Mediterranean Sea is being monitored by vessels on the near horizon.

Among the other countries attending are Canada, China, France, Germany, Japan, Russia, Saudi Arabia and the United Kingdom.

In remarks from the White House shortly after the attacks Obama said, "We're going to do whatever it takes to work with the French people and with nations around the world to bring these terrorists to justice, and to go after any terrorist networks that go after our people."

French President Francois Hollande said Islamic State militants were behind the attacks and the extremist group claimed responsibility Saturday. The U.S. has not yet said whether it believes the group is responsible for the carnage.

Obama’s trip to Turkey will be followed by stops in the Philippines and Malaysia. He's also supposed to travel to Paris in two weeks for a climate conference, though there's now some doubt whether that meeting can take place.

Ahead of Obama's talks in Turkey, Secretary of State John Kerry was meeting in Vienna with his counterparts from Russia, Turkey and other nations with a stake in Syria. The discussions suggest a new seriousness in efforts to end the 4 1/2- year civil war, though how or when that might happen still remains deeply uncertain.

U.S. officials have played down prospects for an imminent breakthrough in Turkey toward quelling Syria's civil war and defeating the militants that have taken advantage of the chaos. Obama's National Security Adviser Susan Rice said the goal was simply to make "incremental progress."

More 250,000 people have been killed in the clashes between rebels and forces loyal to Syrian President Bashar Assad. Eleven million people have been uprooted from their homes, sparking a massive migration crisis in Europe that is also expected to be on the agenda at the G-20 meeting.

Ultimately, Erdogan shares Obama’s desire to remove Assad from his throne in Syria, but the two leaders have disagreed on a plan of action for that.

Erdogan has been frustrated by Obama's willingness to use military force against the Islamic State, but not against Assad. The U.S., meanwhile, was irked by Erdogan's reluctance to join the campaign against the Islamic State, though Turkey eventually decided to start bombing the militants this summer and also allowed the U.S. to launch its own airstrikes from key bases in the county.

Obama's dealings with Russian President Vladimir Putin over Syria have been even more complicated. As Assad's biggest benefactor, Russia has essentially propped up the Syrian leader throughout the crisis. Until Putin is willing to abandon Assad and accept new leadership in Syria, it's unlikely a political solution can be reached.

Despite Obama's vow to isolate Putin in retaliation for Russian aggression in Ukraine, the president agreed to meet with his longtime foe in New York earlier this year to discuss Syria. The slight optimism U. S. officials expressed after the meeting was quickly dashed when Russia began launching its own airstrikes in Syria, raising the prospect of a proxy war with the U.S.

While Putin says his country's forces are targeting the Islamic State, U.S. officials have accused Russia of instead going after forces fighting Assad in a bid to protect the Syrian leader.

Obama and Putin won't hold another formal meeting in Turkey, but White House officials said the leaders would have plenty of time to talk on the sidelines of the G-20.

The Associated Press contributed to this report.