In Orissa, at least five persons, including two women and a three-year-old child, were killed as Maoists blew up an ambulance by triggering a landmine blast in Kandhamal district late last night.Police said, the ambulance was on its way from Gadapur to Brahmanigaon, about two km from the blast site, when it was targetted in the Maoist infested area close to Gajapati and Ganjam.Security forces including CRPF jawans have launched a massive combing operation in the area to nab the Maoists.