China said on Wednesday that operation of its drilling oil rig near the Xisha (Paracel) Islands in the South China Sea is legal and urged Vietnam to stop disturbing China's exploration activities in its territorial waters, the official Xinhua News Agency reported. "The Maritime Safety Administration of China issued navigational notice on May 3 about the oil rig, which belongs to China National Offshore Oil Corporation (CNOOC)," Foreign Ministry Spokeswoman Hua Chunying said at a press conference in Beijing, adding that operation of the drilling rig is lawful in China's territorial waters. "Vietnamese harassment of Chinese companies conducting normal activities runs counter to international law and basic norms of international relations as well as China's sovereignty and administration rights," Hua was quoted as saying.. The US on Tuesday criticized China by calling its exploration activities "provocative and unhelpful to the maintenance of peace and stability in the region." Hua said the Xisha (Paracel) Islands are part of China's inherent territory and the activities of the Chinese companies in the islands are within the mandate of China's sovereignty and administration, which have nothing to do with Vietnam and the US. She said the US is in no position to make irresponsible remarks on China's affairs. China's State Councilor Yang Jiechi had a phone conversation with Vietnam's Deputy Prime Minister and Foreign Minister Pham Binh Minh on Tuesday, demanding that the Vietnamese side stop disturbing Chinese companies' normal work in the Xisha (Paracel) Islands. However, according to a report by Vietnam News Agency on Wednesday, Minh stressed during their conversation that China's unilateral bringing of the rig and a large number of vessels, including military ships, to operate in oil and gas lot on Vietnam's continental shelf was illegal and counter to international law and practice. Minh said that the move had seriously violated Vietnam's sovereignty over the archipelago and its sovereign right and jurisdiction over the country's exclusive economic zone and continental shelf. "Vietnam cannot accept and resolutely opposes China's act and demands that it completely withdraw the drilling rig and escort vessels from the area and hold talks to settle differences around the issue," Minh told Yang.