A retired Taiwanese agent is in police custody for allegedly luring his colleagues to China to force sensitive information out of them, a report said Saturday.

Tung Chien-nan, a former agent at the Investigation Bureau's China situation division, was allegedly recruited by Beijing after his retirement around four years ago, said the United Daily News.

Tung was suspected of tricking several former agents to China under the pretext of travelling or doing business, but they were detained upon arrival on the mainland for interrogation, the report said.

Taiwan's intelligence units are assessing the possible damage Tung has caused. China allegedly used him and other ex-agents to gather information on local spies stationed on the mainland, it said.

The case came to light after another ex-agent who was temporarily held in China reported Tung to Taiwanese authorities. Tung was arrested last month when he returned to Taiwan to collect his pension, the report added.

Taiwan and China have spied on each other ever since they split in 1949 at the end of a civil war. Beijing still claims the island as its territory awaiting reunification -- by force if necessary.

Since 2008, the two sides have seen significant progress when Ma Ying-jeou became Taiwan's president. He was re-elected in January for a final four-year term.

But Ma has said that Taiwan should strengthen its defences against Chinese espionage, following a string of spy scandals that showed intelligence gathering has continued despite warming ties.

Last month, a Taiwanese air force captain was arrested for allegedly leaking classified data to China via his uncle, a businessman based on the mainland.

Taiwan's military court last year handed out life sentences to an army general and an intelligence officer for spying for China in the island's worst spy scandal in recent years.

The Investigation Bureau was not immediately available for comment over the latest case.