China Coast Guard has tracked and monitored two Philippine supply vessels and two coast guard ships which on Tuesday entered waters near the Ren'ai Reef of China's Nansha Islands without the permission of the Chinese government, a spokesman said on Tuesday.

Liu Dejun, spokesman for the China Coast Guard, said in a statement that the four Philippine vessels were warned by the China Coast Guard, which effectively regulated them in accordance with law.

At the same time, regarding the fact that the Philippine ships did not carry illegal building materials for large-scale reinforcement, the Chinese side made "temporary special arrangements" for the Philippine side to transport food and other necessary daily supplies to the "stranded" warship in Ren'ai Reef in a humanitarian spirit, he said. 

"China has indisputable sovereignty over the Nansha Islands and their adjacent waters, including the Ren'ai Reef," said Liu in his statement.

"We firmly oppose the Philippines using the opportunity of transporting supplies to ship illegal building materials to the warship that 'illegally stranded' in the Ren'ai Reef," said Liu. 

Liu added that Chinese Coast Guard will continue to carry out rights protection and law enforcement activities in waters under China's jurisdiction in accordance with law.