Japan called Thursday for international laws to be respected in territorial disputes, as it hosted a symposium in the latest bid to corral global opinion over its rows with China.

"In recent years, we have seen an increase in the frictions and tensions in the seas of Asia," Foreign Minister Fumio Kishida said in a keynote speech at the start of the two-day conference, attended by embassy officials and scholars.

"What's required now for peace and stability in Asian waters is a stricter implementation of rule of law," he said.

The symposium, which involves scholars from China, Vietnam and some Western countries, comes as Beijing is embroiled in a number of disagreements over territory in region.

Beijing and Tokyo are at odds over the sovereignty of uninhabited islands in the East China Sea, which Japan administers and calls the Senkakus but which China claims as the Diaoyus.

Since 2012, Tokyo and Beijing have butted diplomatic heads over the issue, with official Chinese ships and aircraft regularly testing Japanese forces.

On Friday, two Chinese ships entered the Japanese territorial waters of the islands.

The conference is part of Japanese efforts to present its position in the dispute as in line with academic thinking.

On Thursday, Shigeki Sakamoto of Doshisha University in Kyoto, said China needed to be clearer over its claims to a large part of the South China Sea, where it says a "Nine-Dash Line" delineates its "historic waters".

"The questions regarding the legality of the nine-dash line claim should be judged in light of the United Nations Conventions on the Law of the Sea and general international law," Sakamoto said.

So far "China has never provided any explanations," he said.

The Philippines and Vietnam have been the most outspoken countries in the region in criticising China's claims to the sea, which contains major transport routes and fishing grounds and is believed to hold vast mineral resources.

Brunei, Malaysia and Taiwan also have conflicting claims to the waters.