Beijing "does not accept and does not recognise" the ruling by a UN-backed tribunal on its dispute with the Philippines over the South China Sea, the foreign ministry said Tuesday.

The declaration followed a ruling by the Permanent Court of Arbitration in the Hague that China has no historic rights to its claimed "nine-dash line".

"The award is null and void and has no binding force," the ministry said on its website. "China neither accepts nor recognises it."

Beijing "does not accept any means of third party dispute settlement or any solution imposed on China," it added, reiterating its long-standing position on the dispute.

China has repeatedly denied the tribunal's authority to rule on the dispute with the Philippines over the strategically vital region, claiming that the court's actions are illegal and biased against it.

Beijing refused the opportunity to defend its position before the body.

Despite China's assertions, the tribunal's judgement was "very law based," said Julian Ku, an expert on international at New York's Hofstra University, adding that it did "not uncritically accept the Philippines' arguments".

"I was struck by how much the tribunal bent over backwards to give China opportunities to comment and participate in this case," he added.

The dispute has become the centre of a tense standoff between China and the US, with Washington claiming that China's increasingly aggressive behaviour in the region threatens free passage through the area's critically important shipping lanes.

US ships and aircraft have patrolled the region, including passing within the 12 nautical mile limit that would apply to any territorial waters, in what is widely seen as an attempt to undermine Chinese claims of control.

The court ruling, however, has invalidated any claims -- by anyone -- that the reefs and shoals under dispute give such legal rights.

The decision is devastating for China's claims, said Yanmei Xie, China analyst for the International Crisis Group, saying the ruling was "as unfavourable to China as it can be".

Despite the announcement, the Chinese foreign ministry said the country continues to assert it has sovereignty arising from its historical claims.

"China's territorial sovereignty and maritime rights and interests in the South China Sea shall under no circumstances be affected by those awards," the statement said, adding that "China opposes and will never accept any claim or action based on those awards."

China was willing to negotiate directly with other countries "on the basis of respecting historical facts and in accordance with international law", it said, including for joint development.

In the short term, the decision is unlikely to change much, Xie said.

"We're going to see a continuation of the chest thumping we've seen especially from the China side."

Police sealed off the Beijing street where the Philippine embassy stands. More than a dozen white police vans were parked, blocking all entrances to the street, but no protesters were visible.