By Manuel Mogato and John Ruwitch

MANILA/SHANGHAI (Reuters) - Vietnam and the Philippines are determined to oppose Chinese infringement of their territorial waters, Vietnamese Prime Minister Nguyen Tan Dung said on Wednesday, calling on the world to condemn China's actions in a rare public show of unity bound to infuriate Beijing.

China is embroiled in disputes with Vietnam, the Philippines and others over boundaries in the potentially energy-rich South China Sea and has said it seeks to resolve differences in one-on-one talks with the countries involved.

Beijing and Tokyo are also at loggerheads over disputed islands in the East China Sea.

"The president and I shared the deep concerns over the current extremely dangerous situation caused by China's many actions that violate international law," Dung said in a statement after talks with Philippine President Benigno Aquino during a two-day visit to Manila.

"...In particular, China's illegal placement of the oil rig and deployment of vessels to protect the rig deep into Vietnam's continental shelf and exclusive economic zone have seriously threatened peace, stability, maritime security and safety, and freedom of navigation in the East Sea."

Anti-Chinese violence flared in Vietnam last week after Chinese state oil company CNOOC deployed an oil rig 240 km (150 miles) off the coast of Vietnam in waters also claimed by Hanoi. The rig was towed there just days after U.S. President Barack Obama left the region.

The move was the latest in a series of confrontations between China and some of its neighbors. Washington has responded with sharpened rhetoric toward Beijing, describing a pattern of "provocative" actions by China.

"The two sides are determined to oppose China's violations and called on countries and the international community to continue strongly condemning China and demanding China immediately end its violations," Dung said.

Carl Thayer, an expert on Vietnam at the Australian Defense Force Academy in Canberra, said Vietnam had to play what cards it had as it was clear the Association of Southeast Asian Nations (ASEAN) was not going to stand up to China.

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"It's unprecedented for Vietnam to join a U.S. ally and appeal directly for international support," he said. "It is an admission that ASEAN is not going to go to the mat on this one, so Vietnam has got to play some of the only options it has got left."

Dung's harsh words were similar to those he used at a summit of the 10-nation ASEAN in Myanmar this month in which he also urged the international community to protest against China's moves. ASEAN issued a summit communiqué that did not criticize China.

CHINESE PRESIDENT'S WARNING

Chinese President Xi Jinping earlier appeared to warn some Asian nations about strengthening military alliances to counter China, saying this would not benefit regional security.

But he also pledged to peacefully resolve China's disputes over territory, which have intensified in recent years, especially in the South and East China Seas.

"To beef up military alliances targeted at a third party is not conducive to maintaining common security in the region," Xi said in a speech, following a period when some Asian countries have sought to reaffirm their security ties with Washington.

During a visit to Asia last month, Obama also sought to reassure allies such as Japan and the Philippines that his long-promised strategic shift towards Asia and the Pacific, widely seen as aimed at countering China's rising influence, was real.

Xi made his remarks at a regional conference in Shanghai in front of Vietnamese Vice President Nguyen Thi Doan, as well as representatives from the Philippines, Japan and more than 40 other countries and organizations.

His speech was given at a meeting of the little-known Conference on Interaction and Confidence Building Measures in Asia, or CICA.

China has seized upon its hosting of the forum, launched by Kazakhstan in the early 1990s, to try to build clout in the region and beyond. Russian President Vladimir Putin and President Hassan Rouhani of Iran both attended.

State broadcaster China Central Television aired live the arrival of various leaders for the meeting, but underscoring the sensitivity of China's territorial disputes, it cut away from images of Xi shaking hands with the representatives from Vietnam, the Philippines and Japan.

Xi said a zero-sum, "Cold War" concept of security where one country gains at the expense of others would not work.

"We cannot just have the security of one or some countries while leaving the rest insecure," Xi said, adding that "one should not seek the so-called absolute security of oneself at the expense of the security of others".

"No country should attempt to dominate regional security affairs," he said.

(Additional reporting by Greg Torode in Hong Kong and Nguyen Phuong Linh in Hanoi; Writing by Nick Macfie; Editing by Ron Popeski)