SANSHA -- A Chinese research ship was approached and harassed by a military speed-gunboat and a coastguard vessel of the Philippines while conducting scientific research in the South China Sea on Tuesday.

According to personnel aboard the Chinese ship, a speed-gunboat from the Philippine side approached and zigzagged around the Chinese ship Haiyang Dizhi 12, or Ocean Geology 12 in English, in the early morning, disrupting its normal research operations.

Subsequently, vessel No 4411 of the Philippine coastguard crossed in front of the Chinese research vessel and passed through with malicious intent, violating international rules on averting maritime collisions and gravely hampering the safety of the Chinese vessel and its operation.

According to the captain of the Chinese research ship, this was the second time that the Philippine side had harassed China's research vessels since the start of the scientific research mission.

Previously, a Philippine vessel with the number 298 painted on its side deliberately covered the name on its bow, turned off its lighting and automatic identification system, and passed in front of the Chinese research vessel about 300 meters away at a high speed during nighttime, the captain said, noting that the Philippine vessel neither steered to make way nor answered radio communication from the Chinese vessel, posing a serious threat to the latter's safety of navigation.

The Chinese scientific research mission carried out by the ship is based on peaceful purposes and aimed at enriching humankind's scientific knowledge of the ocean, said the chief scientist of this mission, adding that the methods and tools used in the mission are scientific and appropriate.

The mission comply with the general principles outlined in article 240 of the United Nations Convention on the Law of the Sea regarding the conduct of marine scientific research, and are both legitimate and legal, the chief scientist said.

Ding Duo, a researcher with the National Institute for South China Sea Studies, noted that China's marine scientific exploration activities in relevant waters are based on China's territorial sovereignty over the Nansha Qundao and its corresponding maritime rights. China's relevant activities are exercising the rights of coastal countries granted by international laws, including the United Nations Convention on the Law of the Sea, said Ding.

China welcomes scientific research institutions of other countries in the South China Sea to conduct joint maritime scientific research activities with China, promote practical maritime cooperation in various fields, and create favorable conditions for peace and stability in the South China Sea, as well as regional development and prosperity, Ding added.