Leaders from Japan and 10 Southeast Asian countries on Saturday pledged to co-operate in ensuring freedom of navigation during a summit overshadowed by concerns over China's growing assertiveness in the region.

A joint statement refrained from explicit mention of China's declaration of a maritime air defence zone over the East China Sea. But it was the backdrop behind the promise to co-operate to ensure "freedom of overflight and aviation safety in accordance with universally recognised principles of international law".

The summit marks 40 years of ties between Japan and Asean, a resource-rich region of more than 600 million people. Earlier Tokyo pledged 2 trillion ($23 billion) in aid to Southeast Asian nations over the next five years to help close the region's development gap and improve its disaster preparedness. It also promised another 10 billion to support the Japan-Asean Integration Fund.

The Japanese side listed on its "urgent agenda" assistance for improved maritime security and more effective coastguards, help with cybersecurity and counterterrorism, closer communications connections and improved disaster preparedness and management.


China's sudden declaration last month of the air defence zone over islands in the East China Sea that are claimed by both Japan and China raised hackles across the region.

Some worry China might follow up with a similar zone in contested areas of the South China Sea.

"Asean's role as a centre of economic growth depends on freedom of the seas and the air," Japanese Prime Minister Shinzo Abe said.