Philippines increases number of boats on patrol in South China Sea following encounters with Chinese militia vessels

As Beijing's assertiveness continues to grow in the disputed areas of the South China Sea, Philippines has "substantially" increased the number of boats on patrol following encounters with Chinese coastguard and militia vessels, according to a Washington-based think tank.

The Asia Maritime Transparency Initiative (AMTI) of the Center for Strategic and International Studies said that from March 1 to May 25 it had observed "13 Philippine law enforcement or military vessels paying a total of 57 visits to waters around the Spratly Islands and Scarborough Shoal", South China Morning Post reported.

It said this was "a substantial increase over the previous 10 months, when three vessels were tracked making seven total visits to contested features".

In March, tensions between the Philippines and China came to a climax after hundreds of Chinese boats were spotted in the disputed portions of the South China Sea. Philippines defence and foreign ministers have claimed that the "threatening" Chinese vessels are manned by militias.

China claims sovereignty over almost the entire South China Sea and has overlapping territorial claims with Brunei, Malaysia, the Philippines, Vietnam and Taiwan.

The figures, released in a report on Wednesday, were based on "tracking data from commercial provider Marine Traffic and satellite imagery from Maxar and Planet Labs", the think tank said.

Not only were patrols more frequent, but their location had changed to include four disputed features of the sea not visited during the previous period, SCMP reported.

The think tank said that from the satellite data, it could not verify Philippine national security adviser Hermogenes Esperon's May 4 claim that Chinese coastguard and militia vessels were engaging in "dangerous manoeuvres".

However, tracking data showed that when the Philippine coastguard sent four vessels - BRP Gabriela Silang, BRP Sindangan, BRP Habagat, and MCS 3005 - to within 10 nautical miles of Scarborough Shoal, they were met by Chinese coastguard vessels 3301 and 3102.

In the first week of May, Philippine President Rodrigo Duterte had said that he will not withdraw navy and coastguard boats patrolling the disputed South China Sea and insisted that the country's sovereignty over the waters is "not negotiable".

China has been increasing its maritime activities in both the South China Sea and the East China Sea over the past few months, partly in response to Beijing's concerns over the increasing US military presence in the region because of escalating Sino-US tensions.

Beijing's rising assertiveness against counter claimants in the East and South Sea has resulted in unprecedented agreement across the Indo-Pacific.

( With inputs from ANI )