Four people have been killed and two injured -- including a child -- in separate shootings in Thailand's restive south, local police said Monday. They said two men on motorbikes shot dead a 59-year-old pork vendor early Sunday afternoon, while he was riding home with his nine-year-old nephew in Narathiwat province. The child was injured when he fell from the bike. That evening, a 51-year-old construction worker was also killed and his colleague injured in another drive-by shooting nearby. A Muslim defence volunteer was shot dead in the same province later Sunday night while he was parking his motorbike in front of his house. In neighbouring Yala province that night, a group of armed militants raided the house of a 70-year-old man before shooting him dead, police said. More than 3,600 people have been killed and thousands more injured in five years of separatist violence across the three restive provinces of Pattani, Yala and Narathiwat. Buddhist-majority Thailand annexed the ethnic Malay area in 1902, sparking decades of tension.