MANILA: Philippine authorities said Tuesday they detained two Chinese nationals for spying, the latest in a series of arrests involving alleged espionage as confrontations between the countries increase in the disputed South China Sea.

The men allegedly paid a trio of Filipino accomplices to drive them through the capital Manila while using an "IMSI catcher", a device capable of mimicking a cell tower and snatching messages from the air in a 1-3 kilometres radius.

Vehicles carrying the devices were operating near sensitive sites including the presidential palace, the US embassy, Camp Aguinaldo, Camp Crame and Villamor Air Base, according to the National Bureau of Investigation.

NBI agent Ren Dela Cruz told reporters that "thousands" of pieces of data had been gathered before all five men involved were arrested in a Thursday operation.