By Jonathan Head
BBC News, Bangkok
Thai police say they have arrested five army officers over an alleged plot to kill Prime Minister Thaksin Shinawatra.
Explosives were found in a car near Mr Thaksin's home, police say.
Two weeks ago police intercepted a car, driven by one of the officers and carrying a large bomb, near his home.
But opponents have accused Mr Thaksin of fabricating the plot to boost his chances in October's general election.
Opinion is divided between rural voters who praise his policies on the poor, and urban opponents who accuse him of corruption and abuse of power.
The officers accused of this assassination attempt include a major general and a colonel. All come from Thailand's secretive counter-insurgency command, known as ISOC.
If proven, the plot would be an alarming development for a country which put the era of coups and military intervention behind it more than a decade ago.
However there is deep scepticism among the urban middle class in Bangkok. Opinion polls suggest around half the city's population view it as a hoax by the prime minister to boost his popularity.
Security experts are divided. Some believe it was a genuine plot by a disaffected faction in the military, but that the bomb was meant just to scare Mr Thaksin - it was not primed to explode.
These are very tense and uncertain times in Thailand.
Mr Thaksin faces an election battle in October
Despite the annulment, after intervention by the king, of an election called by Mr Thaksin in April, his Thai Rak Thai party is still likely to win a re-run of the ballot thanks to its strong support base in the countryside.
No politician in Thai history has ever matched Mr Thaksin's vote-winning skills.
But his opponents say his abuses of power during his five years in office should disqualify him from office.
Thailand's recently-created democratic institutions have proved unable to adjudicate in this dispute, and it has now drawn in senior members of the military and elite figures close to the king.
The political crisis has until now played out peacefully, but many Thais fear it may be entering a more dangerous phase.