Without naming supporters of the ousted government of then caretaker prime minister Thaksin Shinawatra, Mr Surayud said the attacks were the handicraft of those who had lost power in the coup.
''Based on the government's information and intelligence agencies, it was the work of people who lost power, but I cannot clearly say which group was behind it,'' he said.
Speaking after a meeting with top national security officials, the prime minister said the attacks were carried out to destabilise his government.
''The perpetrators wanted to have a political impact and make Thai people feel political instability,'' he said.
Mr Surayud ruled out the hand of Islamic militants carrying out a violent separatist campaign in south Thailand which has claimed nearly 2,000 lives since early 2004.
''It is very unlikely that it was linked to the southern violence, because it is much easier for the insurgents to mount an attack in the three southern provinces than to target Bangkok,'' he said.
Meanwhile, the ousted prime minister's lawyer issued a statement here on his behalf today denying any involvement in the bombings.
Mr Thaksin, living in England in self-imposed exile since his ouster and presently in Beijing, expressed his sorrow over the incident.
According to his lawyer Noppadol Pattama, Mr Thaksin said, ''He is worried and feels that it is unfair to link him and the old power clique for the bomb attacks.'' The death toll due to bombings rose to three today with one of the victims succumbing to the injuries.