Large protests are taking place on the streets on the Philippine capital, Manila, where leaders are attending the Apec regional trade summit.
Hundreds of people from indigenous, student and labour groups clashed with police, who deployed water cannons.
Though it is not on the agenda, the summit has been overshadowed by territorial disputes between members.
Leaders have also urged for greater global anti-terror co-operation following the Paris attacks.
A draft copy of a declaration due to be released later today says leaders at the Asia Pacific Economic Cooperation (Apec) summit "strongly condemn" all acts of terror and stress the "urgent need for increased international co-operation and solidarity in the fight against terrorism".
The anti-globalisation protesters in Manila were calling for Apec to be dismantled, accusing the trade bloc of taking advantage of poorer countries.
A protest leader, Renato Reyes, told the Associated Press news agency: "APEC and imperialist globalisation have only benefited the rich countries while further impoverishing developing countries like the Philippines."
World leaders at the summit have been discussing issues such as climate change and regional economic co-operation.
But regional defence has cropped up as well, with an ongoing dispute among several Asian countries who have overlapping claims in the resource-rich South China Sea.
US President Barack Obama has called for China to stop its land reclamation work on disputed reefs, and has also signed defence agreements with the Philippines, which has overlapping claims with Beijing.
Chinese President Xi Jinping is also attending the conference but has yet to comment on the issue. China says its work is legal and it has no plans to militarise the new artificial islands.
Mr Obama said there was a need for "bold steps to lower tensions" in the region.
JUSTCLICK & CONNECT