China has sent four oil rigs into the South China Sea in a sign that Beijing is stepping up its exploration for oil and gas in the tense region, less than two months after it positioned a giant drilling platform in waters claimed by Vietnam.
Coordinates posted on the website of China's Maritime Safety Administration showed the Nanhai number 2 and 5 rigs had been deployed roughly between southern China and the Pratas islands, which are occupied by Taiwan. The Nanhai 4 rig was towed close to the Chinese coast.
The agency did not say who owns the rigs.
Earlier this week, it gave coordinates for a fourth rig, the Nanhai 9, which it said would be positioned just outside Vietnam's exclusive economic zone by Friday.
The announcement comes at a time when many countries in Asia, particularly Vietnam and the Philippines, are nervous at China's increasing assertiveness in the South China Sea, where sovereignty over countless islands and reefs is in dispute.
The Global Times, a popular tabloid published by the Communist Party's official People's Daily, quoted Zhuang Guotu, director of the Center for Southeast Asian Studies at Xiamen University, as calling the rig deployment a "strategic move".
"The increase in oil rigs will inevitably jab a sensitive nerve for Vietnam and the Philippines," Zhuang said.