Some of the insurgents blamed for a spiral of violence in southern Thailand were trained in Libya, a senior Thai defence official has claimed.
Security is heavy in Thailand's southern provinces
General Pallop Pinmanee said the militants then used this training to teach many others in the south.
But Thailand's defence minister said there was still no concrete evidence any insurgents had been trained abroad.
He said Mr Pallop's comments were based on "information", not "intelligence information".
The continuing unrest in Thailand's Muslim-majority south has led to the deaths of about 950 people since the beginning of 2004, and shows no signs of abating.
Analysts have long speculated that militants in the region had received outside support.
The Thai government has repeatedly insisted that the insurgency is a local issue, not linked to foreign Islamic groups.
In a telephone interview with the Associated Press on Thursday, Mr Pallop said a group of 20 Thai militants had spent four years in Libyan camps, being trained in combat and bomb-making techniques before returning to Thailand three years ago.
Home to most of Thailand's 4% Muslim minority
Muslim rebels fought the government up to the mid-80s
Suspected militants have upped attacks since 2004, targeting Buddhists
Security forces' response criticised by rights groups
He said the 20 had then trained many more people in the southern provinces of Yala, Pattani and Narathiwat.
But Mr Pallop - deputy head of Thailand's Internal Security Operations Command - denied local media reports quoting him as saying 3,000 Thais had received Libyan training.
Mr Pallop, who is an adviser to Defence Minister Thammarak Isarangkura na Ayudhya, did not explain how he obtained the information.
Mr Thammarak refuted his colleague's comments on Thursday, and so too did US ambassador to Thailand Ralph Boyce.
Mr Boyce told local TV that he saw no evidence of outside funding for the ongoing unrest.
But he warned that the situation could intensify if international militants joined the insurgency.
"Both Thailand and the US have concerns that the situation will develop in such a way, but today we still see the situation as an internal problem," Mr Boyce told reporters after a meeting with Thai Deputy Prime Minister Chitchai Wannasathit.