Thai opposition leader Suthep Thaugsuban said the caretaker government was responsible for the attack on protestors who took part in a march here Friday, and demanded the ouster of Prime Minister Yingluck Shinawatra.
At least 36 people were injured in Friday's bomb blast in the area where protest leader Suthep was holding an anti-government march.
The protestors were demanding that no elections be held until implementation of major political reforms. They have been blocking major road junctions in Bangkok since Jan 13.
Police have raised questions about the incident in which protestors blocked police and reporters from entering the area near the attack scene where they claimed they found a weapons stockpile, the Bangkok Post reported Saturday.
Police also queried the last-minute change in the protest route.
In a speech after the attack, Suthep said the blast that left 36 injured was the work of the government and called on the protestors to draw strength from it.
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"The blood that spilt on the street is piercing my heart. What it (the government) has done to the Thai people is cold-blooded. Let the pain remind us and give us strength to fight until we win," Suthep told protestors.
According to Suthep, the incident showed that the prime minister was not stupid, but a "demon".
Suthep said the attack neither scared him and nor the supporters of the People's Democratic Reform Committee (PDRC) and they would take out another march Saturday in the capital, but gave no details.
He asked the the PDRC to allow police to investigate the incident and promised to improve security in the wake of the blast.
"We have to continue this fight. We have invested a lot in it. Our fellow protestors were injured and killed. This is the 27th assault on us and there have been a lot of injuries," he said.
Meanwhile, Yingluck denied the PDRC's accusation that the government was behind the attack.
Yingluck has called elections Feb 2, but the opposition is boycotting the polls.
Since November, protestors have been taking to the streets and occupying government offices, calling for an end to Yingluck's government.