By Jay Ereno

SOUTH CHINA SEA The Philippines has completed a supply mission for troops stationed in a rusty World War Two-era ship, but not without a usual cat and mouse chase with Chinese vessels in the South China Sea.

Reuters went onboard one of the Philippine Coast Guard's vessels escorting the mission to the Second Thomas Shoal on Friday and witnessed how the Chinese Coast Guard and maritime militia vessels tried to chase and block the Philippine contingent from reaching their destination.

China said the vessels entered the waters without its permission.

During the mission, two Chinese ships blocked two Philippine coast guard vessels. In another instance, a Philippine ship was surrounded by a Chinese coast guard vessel and three maritime militia vessels.

One of the Chinese ships was also seen heading dangerously close to the Philippine vessel which Reuters was onboard, while several Chinese militia vessels tried to block its path.

"We always encounter dangerous manoeuvres, shadowing activities, blocking not only from China coast guard vessels, but also from China militia vessels," Philippine Coast Guard commanding officer Emmanuel Dangate told reporters after the mission.

"It is imperative that the supplies be delivered to BRP Sierra Madre to support our soldiers stationed there."

The Philippines intentionally grounded the warship in 1999 as part of its sovereignty claim to the shoal, which is located inside its 200-mile exclusive economic zone.

China's coast guard said on Friday two Philippine supply boats and two coast guard ships had entered the waters adjacent to the shoal without permission from the Chinese government.

China claims that the Philippines is bringing construction materials that reinforces the rusty warship and violates China’s sovereignty in the shoal. The Philippines says it is taking water and food to its troops.

A U.S. Navy plane was also spotted overhead during Friday's mission.

In a radio message to its Chinese counterpart, the Philippine coast guard warned that the Chinese actions would affect relations between the two countries.

The actions are "illegal, aggressive and destabilising," it said.

It was the second successfully completed resupply mission since Aug. 5 when China's coast guard used a water cannon to deter the Philippine ships.

In 2016, the Philippines won an international arbitration award against China, with the tribunal invalidating Beijing's sweeping claim to sovereignty over most of the South China Sea. Malaysia, Vietnam, Brunei, Taiwan and the Philippines have various claims to certain areas.

(Reporting by Jay Ereño, Writing by Neil Jerome Morales, editing by Clelia Oziel)