Thai security forces killed an alleged separatist militant in a search operation in the country's restive south, while a Muslim man was shot dead in a drive-by attack, police said Monday. More than 300 soldiers, policemen and civil authorities clashed with a group of insurgents during the operation in troubled Yala province Sunday, police said. A 25-year-old man was found dead at the scene and police said he was suspected of involvement in two bomb attacks in the region that wounded 11 people Saturday. Four other people were arrested following the clash, they said. In nearby Pattani province gunmen on motorcycles Sunday shot dead a 50-year-old Muslim man as he was on his way home, police said.