China says the Philippines has occupied Chinese territory in the South China Sea illegally since the 1970s, including Zhongye Island, where Manila has carried out large-scale construction of military and civilian facilities, including airports, ports and barracks.

In January, reports said Manila was planning to install a $1 million satellite-based system on the island to track flights.

Xu Liping, a senior researcher of Southeast Asia studies at the Chinese Academy of Social Sciences, said the Philippine presidential election on May 9 might lead to Manila provoking Beijing on maritime issues.

"On the one hand, the Philippines claims it will resolve the South China Sea issue through peaceful measures, while on the other, it is strengthening military facilities in the region," he said.

The location of Zhongye Island is important, as fighter jets taking off from there can overfly China's Nansha Islands, he said.

Last month, Foreign Minister Wang Yi said China will not accept "tainted" arbitration.

Wang also said that in 2006 China had exercised its right under Article 298 of the United Nations Convention on the Law of the Sea by making a declaration excluding compulsory arbitration.

By not accepting the arbitration case, the Chinese government is acting entirely in accordance with the law, whereas the Philippines' behavior is unlawful, unfaithful and unreasonable, Wang added.

Dispute timeline

Since 1970s:

Philippines seizes eight islands and reefs belonging to China's Nansha Islands.

May 1999:

Philippine ship becomes grounded illegally on China's Ren'ai Reef, reporting a mechanical problem. Manila has refused to remove it.

April 2012:

Philippines sends military vessels to harass Chinese fishing boats and fishermen operating in waters off China's Huangyan Island. The fishermen are badly treated in what becomes known as the Huangyan Island Incident.

January 2013:

Philippines unilaterally initiates an arbitration case regarding its disputes with China in the South China Sea.

March 2014:

Philippine Department of Foreign Affairs issues a public statement declaring its occupation of Ren'ai Reef due to the presence of its grounded ship since 1999.