About 10 armed men on Wednesday entered the homes in the Rangae district of Thailand's Narathiwat province and killed four men, one woman and four children.
Nine others were admitted to the local hospital, police Lieutenant Jenwit Hunsiem said.
Authorities had not yet entered the area where the attack occurred because about 500 villagers had gathered and were blocking them from entering, said Narathiwat Governor Pracha Terat.
"The initial report we've heard is that there are nine people dead in the houses; but authorities cannot enter the area because they fear that the situation will become (violent) like in Tanyonglimo," Pracha told The Associated Press by telephone.
He was referring to an incident in September in Narathiwat's Tanyonglimo district in which two marines were stabbed to death after being held captive overnight by residents who believed they had killed two civilians.
Narathiwat is a Muslim-majority
Efforts to rescue the marines were hindered by women and children in the village who physically blocked outsiders from entering.
"The assailants cruelly murdered these villagers and spread rumours among other villagers that these victims worked for the government," Pracha said of Wednesday's attack.
Thailand's three southernmost provinces - Narathiwat, Pattani and Yala - are the only ones with Muslim majorities in the Buddhist-dominated country.
Muslim residents have long complained of being treated as second-class citizens. More than 1100 people have been killed in separatist violence since early 2004.