Japan and Vietnam agreed Thursday to enhance bilateral cooperation on maritime security, criticizing China for increasingly assertive actions that have led to clashes between Chinese and Vietnamese vessels in the South China Sea.

“I am concerned about tensions in the region resulting from China’s unilateral drilling activity,” Prime Minister Shinzo Abe said at a meeting with Vietnamese Deputy Prime Minister Vu Duc Dam in Tokyo, according to the Japanese Foreign Ministry.

“Japan will continue to underscore the importance of observing law and being ruled by law,” Abe said.

Dam expressed appreciation for Japan’s support, saying Hanoi has been making diplomatic efforts to peacefully resolve the issue and calling for Tokyo’s continued support, the ministry said.

The meeting came after China increased tensions in the sea by deploying an oil rig off the Paracel Islands, which Vietnam also claims, leading to physical clashes between Chinese and Vietnamese vessels.

The development has added to Japan’s concern about Chinese maritime policy at a time when Beijing is regularly sending patrol ships into the territorial waters around the Japan-administered Senkaku Islands, a group of uninhibited islets that it and Taiwan also claim, in the East China Sea.

Abe briefed Dam on Japan’s “policy of proactive contribution to global peace and stability based on international cooperation.”

Dam, who was visiting Japan to attend a forum in Tokyo, conveyed a message from Vietnamese Prime Minister Nguyen Tan Dung expressing that the Southeast Asian country endorses Abe’s policy.

The deputy prime minister also asked for Japanese companies to continue investing in Vietnam.

The clashes in the South China Sea have triggered violent anti-China riots in Vietnam in which some Japanese businesses were mistakenly attacked.

While Abe asked the Vietnamese government to protect Japanese companies in the country, Dam said the government has taken steps to prevent the violence from recurring.

Also Thursday, government sources said Foreign Minister Fumio Kishida is planning to visit Vietnam from late June to early July to promote cooperation on maritime security in the East and South China seas.

At the meeting in Hanoi, Kishida and Vietnamese Deputy Prime Minister and Foreign Minster Pham Binh Minh are likely to agree to speed up consultations on Japan’s provision of patrol ships to Vietnam to address China’s maritime assertiveness in the South China Sea, the sources said.

In reference to China’s muscle-flexing in both bodies of water, Kishida and Minh are expected to affirm that Tokyo and Hanoi will not tolerate any attempt to alter the status quo through coercion or force, according to the sources.

The two ministers are also likely to agree to increase communications with the Philippines and other members of the Association of Southeast Asian Nations to keep Beijing’s territorial ambitions in check, they said.

Claiming the South China Sea almost entirely, Beijing has been asserting control over the land features and waters encompassed by its U-shaped “nine-dash line” in territorial disputes with Brunei, Malaysia, the Philippines, Taiwan and Vietnam.

Kishida and Minh are likely to agree to urge 10-member ASEAN and other regional powers at a regional security forum slated for early August in Myanmar to act in unison in addressing China’s moves.

Kishida might visit Cambodia as well, according to the sources.