Thailand's military-installed government today blamed former politicians for a series of bombs that killed three people in Bangkok, wounded 38, including nine foreigners, and ruined New Year celebrations.
Prime Minister Surayud Chulanont said intelligence pointed to politicians who had lost power, not Muslim militants waging a separatist insurgency in the far south, but admitted the government did not know who was responsible.
Mr Surayud declined to say what evidence pointed to former politicians less than five months after a bloodless coup ousted twice-elected Prime Minister Thaksin Shinawatra, whose supporters he said might have been involved.
The government ruled out any foreign hand in the unprecedented attacks in the Thai capital.
"We could not at this stage pinpoint which particular group was involved," said Mr Surayud, installed after the September coup.
"Briefs from various intelligence agencies, based on evidence available, show that they came from groups that have lost political powers," he told a news conference as police and soldiers mounted a major security operation.
"These were not just the previous government, but include all those which have lost power in the past," he added.
Mr Thaksin's lawyer called the implications a "smear campaign" by the government, which has refused to allow his client to return home to defend himself against corruption allegations.
Australia said it feared more attacks and joined Britain and the United States in urging their citizens to stay indoors.
Involvement of Muslim militants, whose insurgency has cost more than 1,800 lives over the past three years but has remained confined to the far south, was a "very remote possibility", Mr Surayud said.
Coup leader General Sonthi Boonyaratglin, Thailand's first Muslim army chief who cut short his Haj and returned to Bangkok today, ruled out any links to foreign terrorist groups such as al-Qaeda.