BELEK - U.S. President Barack Obama vowed on Sunday to step up efforts to eliminate Islamic State in Syria and prevent it from carrying out attacks like those in Paris, while European leaders urged Russia to focus its military efforts on the radical Islamists.

Speaking at a G20 leaders summit in Turkey, Obama described the killings in Paris claimed by Islamic State as an attack on the civilized world and said the United States would work with France to hunt down those responsible.

The two-day summit brings Obama and fellow world leaders just 500 km (310 miles) from Syria, where a 4-1/2-year conflict has transformed Islamic State into a global security threat and spawned Europe's largest migration flows since World War Two.

"Traditionally the G20 has been a forum primarily to discuss economic issues facing the globe ... (but) the sky has been darkened by the horrific attacks that took place in Paris just a day and a half ago," Obama said in a statement after meeting Turkish President Tayyip Erdogan.

"The United States and its allies will redouble efforts to find a peaceful solution in Syria and prevent Islamic State militants from perpetrating attacks like those in Paris."

Obama and his Western allies now face the question of how the West should respond after Islamic State again demonstrated it posed a threat far beyond its strongholds in Syria and Iraq.(Reuters)