ANTALYA, Turkey — World leaders vowed Monday to boost intelligence-sharing, cut off terrorist funding and strengthen border security in Europe, as they sought to show resolve and unity following the deadly terror attacks in Paris.

“We agreed that the challenge can’t just be tackled with military mean, but only a multitude of measures,” German Chancellor Angela Merkel said.

British Prime Minister David Cameron also announced plans to host a donor conference early next year to raise “significant new funding” to tackle the flood of refugees spilling out of Syria.

“None of this is a substitute for the next urgent need of all: to find a political solution that brings peace to Syria and enables the millions of refugees to return home,” Cameron said.

The leaders of the Group of 20 rich and developing nations were wrapping up their two-day summit in Turkey against the backdrop of heavy French bombardment of the Islamic State’s stronghold in Syria. The U.S. was expanding its intelligence sharing with the French and helping them identify targets, according to American officials.

Numerous meetings about next steps in Syria and the Islamic State campaign were being held on the sidelines of the summit in the Turkish seaside resort of Antalya.

Obama was to huddle with European leaders from France, Britain, Germany and Italy. French President Francois Hollande skipped the summit to stay home and deal with the aftermath of the attacks, but Foreign Minister Laurent Fabius planned to attend the meeting with the U.S. president.

Russian President Vladimir Putin, a key player in ending the conflict in Syria that created a vacuum for the Islamic State, met separately with Italian Prime Minister Matteo Renzi and British Prime Minister David Cameron.

Putin and Cameron both emphasized the need for joint action against terrorism in the wake of Paris terror attack.

“The latest tragic events in Paris show that we have to unite our efforts in fighting this evil, something we should have done long time ago,” Putin said.

Putin launched an air campaign in Syria a month-and-half ago with the Islamic State as the top declared target. The U.S. and its allies, however, have accused Moscow of focusing on other rebel groups in a bid to shore up Syria’s leader Bashar Assad, whom the West sees as the main cause of the Syrian conflict and the chief obstacle to peace.

Nearly five years of clashes between Assad’s forces and opposition groups have left more than 250,000 people dead, created a vacuum for the Islamic State and other extremists groups to thrive, and spurred a massive refugee crisis in Europe.

Ahead of the G-20, foreign ministers met in Vienna to discuss a new diplomatic plan to end the Syrian war. The plan appears to be based largely on a Russian proposal that envisions negotiations between Assad’s government and opposition groups starting by Jan. 1.

Still, sharp differences over Assad’s future and disagreements about what militant groups in Syria should be considered terrorists have dampened hopes for a breakthrough.

The Vienna talks were high on the agenda when Obama and Putin huddled for about 35 minutes Monday on the sidelines of the G-20.