Four people were killed when a military helicopter crashed during a training flight in Kazahkstan on Wednesday, a report by the Interfax news agency quoting officials said. The Mi-17 helicopter had been on approach to an air force base near the capital Astana when it exploded in mid-air, the report said. The victims reportedly included a three-man crew and a bodyguard for President Nursultan Nazarbayev. Police and troops surrounded the crash site, Interfax said.