The terror attacks in Paris will be among the issues G20 leaders will be discussing when they meet for a summit in Turkey today.
President Obama has already arrived, but French President Francoise Hollande will not be attending.
British prime minister David Cameron, Russian president Vladimir Putin and Japanese prime minister Shinzo Abe are among the other leaders in attendance, along with Turkish prime minister Recep Tayyip ErdoÄŸan.
Thousands of police and security personnel have been deployed to guard the Antalya summit.
Leaders of the world's 20 biggest economies will also be talking about economic and tax cooperation, climate change, and the response to the actions of Islamic State.
It is understood the leaders of the world's 20 most powerful countries have agreed to step up border controls and airport security following the Paris attacks.
US President Barack Obama has pledged to help hunt down the masterminds of the Paris attacks and bring them to justice:
The summit will include talks about tax avoidance by multinationals like Starbucks, Amazon and Google.
However Anders Dahlbeck from the development aid charity Action Aid says the current proposals do not go far enough:
