US President Barack Obama has described the killings in Paris claimed by Islamic State as an attack on the civilised world.
He says the United States will work with France to hunt down those responsible.
"As we, I'm sure, each said to (French) President Hollande and the French people, we stand in solidarity with them in hunting down the perpetrators of this crime and bringing them to justice," Obama told a joint news conference with Turkish President Tayyip Erdogan on Sunday ahead of a G20 leaders summit.
Obama also condemned a double suicide bombing linked to IS in the Turkish capital Ankara last month, after a meeting with Erdogan at which the two leaders discussed the conflict in Syria, efforts to tighten Turkey's borders, and the refugee crisis affecting Turkey and Europe.
"As was true with the terrible attacks that took place in Ankara, the killing of innocent people based on a twisted ideology is an attack not just on France, not just on Turkey, but it's an attack on the civilised world," Obama said.
He said Turkey had been a "strong partner" with the US-led coalition in going after IS in Syria and Iraq.
"The discussion we had today I think was very helpful in helping continue to coordinate work that we are doing together, to help to fortify the borders between Syria and Turkey that allow Daesh (IS) to operate," Obama said.
Erdogan said Turkey, which holds the G20 presidency this year, would continue to show solidarity with the US and said he expected the summit to produce a strong statement on the fight against terrorism.
"We are confronted with collective terrorism activity around the world as terrorism does not recognise any religion, any race, any nation or any country," Erdogan said.
"We will of course carry on with our discussions in the G20 summit within the predetermined agenda, however we will put strong emphasis on having a firm stance on international terrorism," he said.
