A Navy report said about 10 Chinese boats and four Vietnamese vessels laid anchor off three islands occupied by Philippine troops.
Several vessels were seen in Pagasa or Thitu island and one each off in Lawak or Nanchan and in Ayungin or Second Thomas shoal, the report added.
The report said the four Vietnamese vessels were seen off the islands of Parola or Northeast Cay, Lawak, and Rizal or Commodore reef between March 31 and April 13 this year.
The report said the Vietnamese vessels were not trawlers but cargo ships.
Some of the vessels are still in the area, while the others had already left, the report added.
The report was released at a time when military authorities suspect the Chinese of upgrading communications facilities on Mischief Reef, which is within the country’s 200-mile exclusive economic zone.
However, Defense Secretary Angelo Reyes said last week Air Force reconnaissance photographs showed that facilities had "only been repainted" and not upgraded.
Pagasa, the largest of the Philippine-controlled islands, is garrisoned by Marines, Navy and Air Force troops. It also has a runaway long enough to accommodate a C-130 cargo plane.
A Navy ship has remained aground off Ayungin shoal since May, 1999. It is located near Mischief Reef, which is about 120 nautical miles off Palawan. Mischief is being claimed by the Philippines and China. – Paolo Romero