Three vessels from the Chinese coast guard and one vessel said to be part of China’s naval militia were seen installing the roughly 300-meter-long barrier at Scarborough Reef, a Philippine coast guard spokesman said in a statement.
The Philippine Coast Guard and Fisheries Authority call the action illegal and dangerous.
Tensions have increased in recent years around the South China Sea. China claims almost the entire sea, but Brunei, Malaysia, the Philippines, Taiwan and Vietnam also believe they are entitled to parts of the fish-rich and commercial waters.