Bangkok remains on high alert

In a letter sent from Beijing, Mr Thaksin said the attacks on New Year's Eve bore all the hallmarks of Muslim militants fighting in the south.

PM Surayud Chulanont has already said it is unlikely insurgents are to blame.

On Monday, he suggested "groups that have lost political powers" were behind the attacks, without giving names.

"These were not just the previous government, but include all those which have lost power in the past. We could not at this stage pinpoint which particular group was involved," he said.

A number of people linked to the government of Mr Thaksin, which was deposed in a bloodless coup in September, have been questioned over the attacks.

'Olive branch'

Thaksin Shinawatra, who is in exile in China, insisted he played no part in the attacks and accused the government of rushing to conclusions.

Hunt for the bombers Blasts in pictures

"I strongly condemn this act [of bombing] and I swear that I never ever think of hurting the people and destroying the country's credibility for my own political gain," he said in a handwritten letter given to reporters.

He said the bombing bore similarities to previous attacks linked to the insurgency, which has killed more than 1,500 people in the restive south in three years.

And he suggested the new leadership - which has shifted away from his widely-criticised hardline approach to the insurgency - had political reasons for not wanting to make the link.

"If the government did admit that, it would show the failure of their new 'olive branch' approach to the conflict," he said.

Injuries

Security has been high in Bangkok, with a heavy police presence at bus and train terminals as well as the new airport, as people returned from New Year breaks.

No-one has yet admitted responsibility for the eight blasts which hit the Thai capital as revellers filled the streets for New Year's Eve.

Two people died on Sunday, and a third man died of his injuries in hospital on Monday. All three victims were Thai.

Several foreign tourists were hurt, including two British men, three Hungarians, two Serbs and an American.

The attacks have shaken a country that is traditionally seen as one of the safest in Asia.

But although people have been advised to stay at home and avoid moving about, particularly in areas with large crowds, few are heeding the advice and life appears to be getting back to normal.

The attacks could impact on the economy, although the extent of the damage will remain unclear until the nation's stock exchange reopens on Wednesday.