Taipei says it can play an important role in territorial disputes in the South China Sea, and that rival claimants such as the Philippines and Vietnam have tried to persuade it not to side with Beijing. Taiwan's security chief, Tsai Der-sheng, said on Monday it was able to use islets it controlled in the South China Sea to gather intelligence about the latest situations, and had also carried out an oil exploration project in the region without obstruction from other claimants. Tsai's comments followed criticism by Taiwanese legislators on Monday that the government of mainland-friendly Taiwanese President Ma Ying-jeou had been silent on the South China Sea during the recent stand-off between Beijing and the Philippines over the sovereignty of the Scarborough Shoal, known as Huangyan Island in China and as the Panatag Shoal in the Philippines. For years, the potentially oil-rich South China Sea region has been claimed in part or in whole by Taiwan, mainland China, Brunei, Malaysia, the Philippines and Vietnam. Tension has escalated since April 10 when a stand-off began between Beijing and Manila at the Scarborough Shoal, which is within the Philippines' 200-nautical-mile exclusive economic zone, but is claimed by China. 'Had we played no role in this, officials from the Philippines, Indonesia and Vietnam would never have publicly or privately persuaded us not to work with the mainland on the issue,' Tsai told the legislators. 'This shows that those countries are aware of the existing force and values of Taiwan.' Asked what Taiwan's stance was, Tsai said 'it is our unwavering stance that we will not co-operate with the mainland on the issue'. On April 25, Fan Liqing , a spokeswoman for the State Council's Taiwan Affairs Office, said in Beijing that people on both sides of the Taiwan Strait should share responsibility for safeguarding the sovereignty of islands in the South China Sea and their adjacent waters. She also said it would be a good idea for the two sides to engage in joint development of the region. Tsai said that in order to increase Taiwan's understanding of the situation in the region, it had taken more surveillance images using devices the Taiwanese had installed at Taiping Islet, the largest of the disputed Spratly Islands group, which is controlled by Taiwan. He also said the ongoing oil-exploration project carried out by Taiwan's Chinese Petroleum Corporation near Taiping Islet had met with no obstruction from other countries, indicating Taiwan's active presence in the region. In addition to Taiping Islet, Taiwan also controls nearby Ban Than Reef and Pratas Island. On Monday, Lin Yu-fang, a legislator for the ruling Kuomintang, asked the government to build permanent infrastructure on Ban Than Reef, saying there had been growing signs of Vietnam's intrusion into surrounding waters. Taipei has repeatedly maintained that the South China Sea disputes should be resolved by peaceful means and joint exploration of resources in the region. Ma reiterated his government's stand shortly after he was sworn into office for a second four-year term on Sunday.