MANILA - The Philippines' defense chief on Tuesday ordered the military to investigate a report by a US-based tech firm that hundreds of Chinese vessels were dumping sewage into contested areas of the South China Sea.

China maintains a constant presence of coastguard and fishing boats in the South China Sea to assert its claim of sovereignty, including hundreds in the Spratly islands, where the Philippines, Brunei, Taiwan, Vietnam and Malaysia also have claims.

Simularity, an AI-based satellite image analysis firm, on Monday made public satellite images over a five-year period that it said showed damage caused by untreated human waste from Chinese vessels.

• Dumped human waste from Chinese ships creating 'dead zone' in Spratlys - intelligence firm

"While we are confirming and verifying these wastes being dumped ... we consider such irresponsible acts, if true, to be gravely detrimental to the marine ecology in the area," Philippine Defense Secretary Delfin Lorenzana said in a statement.

"Despite conflicting claims and interests by states in the South China Sea, all nations must be responsible stewards of our natural resources and environment."

At a forum on Monday, Liz Derr, Simularity co-founder and CEO, said the waste could threaten fish stocks.

"It is so intense you can see it from space," Derr said.

The Chinese embassy in Manila did not immediately respond when asked by media for comment on Simularity's report.

The Philippines has become more vocal in recent months over the presence of hundreds of vessels it believes are Chinese maritime militias.

• Philippine coast guard disperses 5 Chinese, 2 Vietnamese vessels in WPS

RELATED VIDEO

Watch more in iWantv or TFC.tv