Kolkata, Dec 5 (PTI) West Bengal Chief Minister and Trinamool Congress chairperson Mamata Banerjee on Sunday demanded a thorough investigation into the killing of at least 11 civilians by security forces in Nagaland. At least 11 daily wage labourers were gunned down by security forces in Nagaland"s Mon district while they were returning home from work at a coal mine on Saturday evening, police said, adding that it was investigating whether the incident was a case of mistaken identity. "Worrisome news from #Nagaland. Heartfelt condolences to the bereaved families. I pray for the speedy recovery of those who were injured. We must ensure a thorough probe into the incident and ensure that all victims get justice!" Banerjee tweeted. Army personnel, while conducting an operation after receiving inputs about the movement of militants belonging to the Yung Aung faction of proscribed outfit NSCN (K), opened fire on the pick-up truck in which the labourers were travelling, police said. Army expressed regret over the incident and ordered an inquiry, while also stating that one soldier was killed and several others were seriously injured. Nagaland Chief Minister Neiphiu Rio promised a high-level probe into the incident and appealed to all sections of the society to maintain peace. PTI SUS ACD ACD