Officials in southern Thailand say gunmen opened fire inside a mosque during evening prayers, killing at least 11 people and wounding at least 12 others.
Police initially said five men carrying assault rifles on Monday evening sprayed the worshippers with bullets.
But a military official later said there were only two attackers.
One of the dead was the imam of the mosque in Narathiwat province.
No one has claimed responsibility for the attack.
Army spokesman Colonel Parinya Chaidilok said the attackers appeared to be trying to make it look as though Thai security forces were responsible. He said it was impossible that the military was involved.
In separate news, a Thai soldier died in a bomb blast and suspected militants shot and killed a rubber tapper in Thailand's troubled southern provinces.
On Sunday, suspected Islamist insurgents opened fire in a residential area of Narathiwat province, killing a volunteer patroller. Officials said a car bomb went off in the same area a few minutes later, killing another villager and wounding 19 others.
On Saturday, officials said a teacher was shot dead in neighboring Pattani province.
An Islamic insurgency in southern Thailand has targeted at the area's Buddhist minority and local Muslims who support the government.
The population of Pattani, Narathiwat and Yala provinces is mostly Muslim, while the remainder of the country is predominantly Buddhist.
More than 3,700 people have died since the insurgency began in 2004.
Some information for this report was provided by AFP, AP and Reuters.