ANKARA, July 7 (Reuters) - NATO Secretary General Mark Rutte said on Tuesday that allies buy up to five Northrop Grumman MQ-4C Triton high altitude surveillance drones, with Norway, Finland, Germany and Denmark signing a letter of intent for the purchase. This is the first purchase of Triton drones by the alliance and will complement NATO’s current fleet of RQ-4D Phoenix intelligence, surveillance and reconnaissance drones based at Sigonella Air Base in Sicily, Italy.