The opposition Puea Thai MP and red-shirt leader Jatuporn Promphan on Thursday said the people behind the three unexploded bombs found in Bangkok and Nonthaburi on Wednesday were just providing an excuse for the government to maintain a state of emergency in the capital, Thai media reported.

Bangkok Post online quoted him as saying the perpetrators intend to incite unrest to prevent a general election, as the anti- government red-shirts urged the government to do in their chronic rally from mid-March to mid-May.

These are similar to the planting of the grenade which exploded near the King Power duty-free complex in Bangkok, he said.

On Wednesday night the police found two bombs in Nonthaburi, a province neighbouring Bangkok, and a third one near Santiratwitthayalai school in Bangkok. They were all safely defused.

The two explosive devices found in Nonthaburi -- one found at a parking lot of the Mall shopping centre on Ngamwongwan Road and another at the parking lot of the Public Health Ministry -- and the one in Bangkok were all assembled in a similar manner, each having a timing device and explosives put in a fire extinguisher as shell, police said.

Police said the improvisation of fire extinguishers as bombs was found during the red-shirts rally in Bangkok from March to May, during which the conflict between red-shirts and security forces killed 91 and injured 1,900. Bangkok and some other provinces have been under the state of emergency since April 7.

Pol Maj Gen Panupong Singhara na Ayutthaya, an adviser to the Royal Thai Police, said on Thursday that judging from the components of the explosives and how they were put together, it can be concluded the bombs were made by the same group of people.

Police believe the people behind the bombs have the intention to cause panic in society, he said.

This was after two bombs, wrapped in newspaper, was found on the street in Pattaya, a coastal resort city 150 km east of Bangkok, on Monday.

After Bangkok saw two bombing attacks in the end of August, the Centre for the Resolution of the Emergency Situation (CRES) has step up security measures by keeping 24-hour alert on 454 spots across the capital city.

The state-run National Broadcasting Services of Thailand (NBT) was attacked by an M79 grenade on August 31. There were no casualties, only damaging property. And on August 27, a security guard was seriously injured when a bomb went off near a duty-free shop, King Power complex, in central Bangkok.