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.
