By Kate McGeown
BBC News, Bangkok
The people of Bangkok have woken up to a new year and a new reality - the fact that their normally safe city has been subjected to a series of bomb attacks.
The bombings have stumped the Thai authorities so far
At least eight blasts exploded across the Thai capital late on Sunday, killing three people and injuring at least 30 others, including foreign tourists.
"What happened is completely unprecedented," said Thitinan Pongsudhirak, a professor of political science at Bangkok's Chulalongkorn University.
Thailand is normally seen as one of the safest countries in Asia, and so the question that many of the capital's citizens are now asking is who would want to do something like this.
No-one has claimed responsibility, but two main explanations have been put forward.
One lays the blame on Islamic insurgents from the south, keen to widen their campaign for autonomy, while the other blames elements loyal to former Prime Minister Thaksin Shinawatra, who was ousted in a coup four months ago.
Initial speculation pointed to a possible link with the south because the insurgents there sometimes use similar types of bombs to those used on Sunday.
And while they have so far confined their attacks to the provinces bordering Malaysia, these militants have never ruled out the possibility of extending their campaign to other parts of the country.
But the theory of Islamic insurgent involvement has now been largely discounted.
"The blasts in Bangkok were too well-organised," said Chidchanouk Rahimmula, a lecturer of political science at the Prince of Songkhla University in the southern province of Pattani.
"The insurgents from the south don't have the capacity to launch such a large-scale attack outside their own region," she said.
The government seems to agree. "From the evidence we have gathered, there is a slim chance that [Sunday's violence] is related to the southern insurgency," Prime Minister Surayud Chulanont told reporters on Monday.
Instead, General Surayud blamed "groups that have lost political powers".
He did not explicitly mention the previous government of ex-Prime Minister Thaksin Shinawatra, but he did not need to - the link was only too obvious.
Many analysts agree with his stance. "This is all about Thaksin against the current establishment," said Mr Thitinan.
The attackers "wanted to discredit the new government, and make the military look weak," he said.
Mr Thaksin's regime was ousted by the military last September, and replaced by General Surayud's government - a caretaker administration that will hold office until a new constitution has been written and democratic elections take place.
But the flamboyant Mr Thaksin - who is currently thought to be in China, having been advised against an imminent return to Thailand - still has a significant amount of support in his homeland, especially in the rural north.
More than a dozen schools in the north-east have been torched in recent months, in what is assumed to be a protest against the new regime.
And despite pressure from the media and human rights groups, the government has kept martial law in place in some areas, because of what it calls "undercurrents" of instability.
At least eight blasts rocked Bangkok on New Year's Eve
Support for the old regime has also been enhanced in recent weeks by a series of problems to have beset Mr Surayud's government.
Last month's stock market crash left investors feeling less confident of the ruling administration, and there have been signs that the military is still in overall control despite the appointment of a civilian government.
The new regime has also failed to lay any definite charges against Mr Thaksin and his close allies - despite citing government mismanagement and corruption as the main reasons for the coup.
While it therefore seems plausible that Mr Thaksin's supporters might have had a hand in the events on Sunday night, there is so far no evidence as to who these people might be.
Mr Thaksin's lawyer, Noppadon Pattama, was quick to deny that his client had anything to do with the attacks, saying he was the victim of a "smear campaign".
But Mr Thitinan says that, while Mr Thaksin is unlikely to have been behind the blasts, "elements of the former regime" could well have been involved in some way.
In a possible sign that the government also believes this, several senior aides to Mr Thaksin were ordered to report to the military on Monday - although the meeting was later cancelled.
But whatever his suspicions, even Mr Surayud has had to concede that the identity of the culprits is still far from obvious, admitting to reporters that he could not "pinpoint which particular group was involved".
Speculation is rife, with some people even suggesting that the coup leaders themselves were behind the blasts, in an attempt to discredit Mr Thaksin and encourage Thais to back a strong military leadership.
Amongst all this uncertainty, one thing is clear - the fact that bombs have gone off in the party-loving, traditionally safe Thai capital will have a profound effect on the psyche of the people living here.
It is also likely to be detrimental to the economy, tourism and foreign investment.
Thailand had a turbulent 2006 - with street protests, an election that was subsequently invalidated and then a military takeover - and if Sunday night is anything to go by, 2007 could well continue in the same vein.