Thaksin supporters had earlier in the day issued an ultimatum to the Council for National Security to step aside and let the former prime minister return to power. Prayuth said the military had a backup plan in case protest-leaders broke their promise not to take to the streets.

Thaksin followers were reportedly going to march to Privy Council chief Prem Tinsulanonda's residence and call for him to resign. Last Saturday they trooped from Sanam Luang to Army headquarters on Rajdamnoen Avenue.

Prayuth denied that the military planned to organise mobs of protesters to clash with pro-Thaksin organisations so as to justify drastic action against them.

"We cannot do that. Security officials have to avoid that, because it would cause the incident to escalate," he said.

If the situation does not turn violent and chaotic, as for instance with protesters setting property on fire or storming state offices, there is no need to declare a state of emergency, he said, but if protest leaders incite the crowd to instigate violence, the government will have to do so.

The Army has joined forces with police to protect all government offices along Rajdamnoen Avenue.

Council for National Security chief General Sonthi Boonyaratglin will take charge of overall security and keep in touch with Prime Minister Surayud Chulanont. The First Army Area, which oversees the capital, will take orders from Sonthi, Prayuth added.

CNS spokesman Colonel Sansern Kaewkamnerd said security officials had been instructed to communicate politely with protesters and avoid confrontation.

"If there's a scene anywhere, officers will defuse the situation case by case," he said.