They say the information came from the plane's flight data recorders, which are being analysed by British experts. However, it remains unclear who fired a missile, with pro-Russia rebels and Ukraine blaming each other.
There were 298 on board the MH17 plane. No body survived.
Dutch investigators leading the inquiry into the crash have refused to comment on the Ukrainian claims.
Heavy fighting has prevented an international police force comprising Dutch and Australian officers from reaching the crash site for a second consecutive day.
Earlier, UN human rights chief Navi Pillay said the downing of the Malaysia Airines jet could constitute a "war crime".