Four people were killed and four injured in a bomb blast in Thailand’s restive deep south, police said Friday, the latest unrest in a region wracked by a violent insurgency for more than a decade.

Four people were killed and four injured in a bomb blast in Thailand's restive deep south, police said Friday, the latest unrest in a region wracked by a violent insurgency for more than a decade.

The explosion hit a checkpoint in Khok Pho district of Pattani province on Thursday evening, killing four men aged between 43 and 54.

"Four village defense volunteers were killed and four wounded, who are still hospitalized," local police Colonel Uthai Thipsopa said from the blast site.

In recent years Thai authorities have armed village volunteers to protect their hamlets from frequent gun and bomb attacks by Malay rebels seeking greater autonomy.

More than 6,400 people have been killed in the conflict - the majority civilians - since 2004.

Authorities stand accused of perpetrating severe rights abuses, including arbitrary arrests and extrajudicial killings.

Rights groups have previously expressed fears that arming local volunteers promotes vigilantism in a region already scored by suspicion and impunity for civilian deaths.