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 kilometre (about 3,200-9,800 feet) 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.

"These individuals were conducting covert and unauthorised intelligence gathering activities, posing a threat to national security," Colonel Xerxes Trinidad, Philippine military chief of public affairs, told reporters.

A Filipino driver produced by authorities at Tuesday's press briefing said he had been working with the men since October, and paid 3,000 pesos (about $52) a day for driving around the capital with "the box turned on".

As with six arrests made last month, officials declined to say for whom the electronically recorded information was intended.

In late January, local security officials said they had taken five alleged Chinese spies into custody. Two of the men were arrested for allegedly using a drone and high-resolution solar-powered camera to record activities at a naval base and other locations.

And earlier in January, police arrested a Chinese software engineer named Deng Yuanqing who was suspected of spying on military and police camps -- allegations that were denied by China.

The Chinese and US embassies did not immediately reply to requests for comment on Tuesday.

Confrontations between the Philippines and China over contested reefs and waters in the strategic South China Sea have escalated in recent months.

Beijing claims most of the strategic waterway despite an international ruling that its assertion has no legal basis.

Philippine Chief of Staff General Romeo Brawner last month said it was premature to conclude that the spying was state-sponsored, with Filipino authorities yet to identify the end-receiver of the intelligence gathered.