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.

Both the Triton and the Phoenix drones would be used for NATO’s ground surveillance programme. Both the drones are based on Northrop’s Global Hawk which has a wingspan of 35.4 meters (116 feet) and can stay aloft for more than 30 hours.

Speaking at a defence industry forum ahead of the NATO summit in Ankara, Rutte said intelligence, surveillance and reconnaissance were crucially important for the alliance.

(Reporting by Sabine Siebold, Mike Stone and Tuvan Gumrukcu; Editing by Andrew Heavens)