More attacks on the government are anticipated in the very near future, Thailand's prime minister said Thursday after three unexploded bombs were found at different locations in Bangkok and a nearby province Wednesday night.

"Many people, including myself, have assessed the situation and decided we'll have to be more cautious over the next two weeks," Abhisit Vejjajiva said, adding the perpetrators wanted the attacks to be symbolic, to mark the fourth anniversary of the September- 19th coup, which toppled the then Prime Minister Thaksin shinawatra.

Meanwhile Suthep Thuagsuban, Deputy Prime Minister for security affairs, said on Thursday that he had ordered strengthened security at key government offices, private buildings and important figures' residences after the explosive devices were found and reports of possible assassination reached.

Suthep gave the orders based on a police report that warned of possible assassination of key persons including Abhisit, Suthep himself and the Commander-in-Chief of the Royal Thai Army Anupong Paochinda. Suthep said, however, everyone on the "risk list" is being careful but continues to work as normal.

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

The two explosive devices found in Nonthaburi province -- 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 found 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.

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.

On the other hand, the opposition Puea Thai MP and red-shirt leader Jatuporn Promphan on same day said the people behind the three unexploded bombs just want to provide an excuse for the government to maintain a state of emergency in the capital, Thai media reported.

Bangkok and some other provinces have been under the state of emergency since April 7 in the face of the then ever-escalating rally.

Bangkok Post online quoted him as saying the perpetrators intend to incite unrest to prevent a general election, as the red- shirts urged the government to do during their rallies.

Abhisit, in his comment on the bombs, denied the accusation that the government was trying to create a scenario, or to incite violence, as an excuse to extend the lifespan of the emergency decree, which remains to rule Bangkok and six other provinces three months after the anti-government rally by red-shirts finished on May 19.

"The political situation has intensified and there are people who do not want to see reconciliation in the country," Abhisit said.

Those behind the violence wanted to link the attacks of the past few days with political factors. The political sector must shake off their plot, Abhisit said.

Suthep said he has also instructed the police to tighten security although there has been no concrete information from intelligence agency whether violence may occur during the red- shirts' demonstration on September 19.

The red-shirts, many of the group being the supporter of Thaksin, has announced to stage their rallies in Bangkok and Chiang Mai that day to mark the 4th anniversary of the coup.

Thailand has seen several bombing attacks or attempts in the past two weeks. Two bombs, wrapped in newspaper, was found on the street in Pattaya, a coastal resort city 150 km east of Bangkok, on Monday.

The headquarters of the state-run National Broadcasting Services of Thailand (NBT) in Bangkok was attacked by an M79 grenade on August 31. There were no casualties, only damaged 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.

The Centre for the Resolution of the Emergency Situation (CRES) has step up security measures across the capital city by keeping 24-hour alert on 454 spots across Bangkok since September 3.