A rules-based maritime order is key to protecting the oceans and seas, top coast guard officers from over 30 nations - including the US, China and Singapore - agreed yesterday.

This comes as Tokyo hosted the first Coast Guard Global Summit, in a departure from previous coast guard meetings that have been held only at the regional level.

"Strengthening cooperation between maritime security agencies and increasing dialogue is required now, to cope with the stiffer challenges facing the world today," Japanese Minister of Land, Infrastructure, Transport and Tourism Keiichi Ishii said at the summit.

These challenges, laid out in a 12-point summary after a day of closed-door sessions, include coping with climate change, migration, overfishing, terrorism and piracy, as well as improving distress and disaster response.

But what was not explicitly discussed were specific issues like the threat of North Korean missiles falling into open waters, and sovereignty disputes in the East and South China Seas.

The summit came days after Japan on Monday marked five years since it nationalised the disputed Senkaku islands. Chinese Coast Guard vessels have frequently entered Japanese territorial waters near the islands as signs of protest.

At a news conference on Monday, top government spokesman Yoshihide Suga issued a stiff rebuke, saying: "The repeated incursions into our territorial waters is truly regrettable... We would like to handle the situation firmly and calmly."

China has chafed at international criticism that it has been ignoring the rule of law at sea, in its unilateral construction of military assets in the South China Sea where four Asean nations have overlapping claims.

Japanese Prime Minister Shinzo Abe had said at a reception welcoming the guests on Tuesday that forming common values and bonds via an international summit at a time of stiffer challenges is akin to "a lighthouse shining in the dark ocean".

Dr Heng Yee Kuang of the University of Tokyo told The Straits Times: "Tokyo has long relied on its coast guard as a non-military tool to enhance its regional presence and security profile."

Such a multilateral forum, he added, would be useful for Japan to "minimise any potential residual concerns about Japan being once again an active security actor".