Singapore's Foreign Ministry issued a statement in which it expressed surprise at comments last week by Council for National Security chief General Sonthi Boonyaratglin that the island state could be listening to confidential calls here.

"We do not know what General Sonthi's remarks meant. Domestic calls within Thailand are not routed through Singapore," said the statement issued late on Monday.

"It does not make business or technical sense to route domestic calls via another country. Doing so will incur additional and unnecessary network resources, including costly international bandwidth, and degrade the quality of service."

General Sonthi has said the military would consider reverting to use of two-way radios for sensitive calls after voicing concern over foreign ownership of Thai telecom firms.

Thailand's biggest mobile phone operator, AIS, is a subsidiary of Shin Corp, the telecom giant that Thaksin sold to Singapore's state-linked Temasek Holdings in a controversial tax-free deal last year. The junta chiefs have reportedly already stopped using AIS's mobile phone system.

"The armed forces are currently experiencing a problem. We pick up the phone and the line runs to Singapore. We can talk about confidential official matters, but it goes to Singapore," Sonthi said.

Communications minister Sitthichai Pokaiyaudoom also summoned executives of Shin Satellite, which transmits mobile phone signals, and told them to reject any requests to tap phones.

But the Singapore Foreign Ministry said: "As an international telecommunications hub, Singa-pore maintains a strict and professional operating environment to safeguard the integrity of all communications which terminate in or transit through Singapore."