Didn't expressly say so
Article 5
The Parties agree that an armed attack against one or more of them in Europe or North America shall be considered an attack against them all and consequently they agree that, if such an armed attack occurs, each of them, in exercise of the right of individual or collective self-defence recognised by Article 51 of the Charter of the United Nations, will assist the Party or Parties so attacked by taking forthwith, individually and in concert with the other Parties, such action as it deems necessary, including the use of armed force, to restore and maintain the security of the North Atlantic area.
Any such armed attack and all measures taken as a result thereof shall immediately be reported to the Security Council. Such measures shall be terminated when the Security Council has taken the measures necessary to restore and maintain international peace and security .
But 2 things you need to consider, that's Article 6 and 7
Article 6
For the purpose of Article 5, an armed attack on one or more of the Parties is deemed to include an armed attack:
- on the territory of any of the Parties in Europe or North America, on the Algerian Departments of France 2, on the territory of Turkey or on the Islands under the jurisdiction of any of the Parties in the North Atlantic area north of the Tropic of Cancer;
- on the forces, vessels, or aircraft of any of the Parties, when in or over these territories or any other area in Europe in which occupation forces of any of the Parties were stationed on the date when the Treaty entered into force or the Mediterranean Sea or the North Atlantic area north of the Tropic of Cancer.
Article 7
This Treaty does not affect, and shall not be interpreted as affecting in any way the rights and obligations under the Charter of the Parties which are members of the United Nations, or the primary responsibility of the Security Council for the maintenance of international peace and security.
Article 6 lay out where the attack occur would lies within the responsibility of Article 5. Not sure how Greek Island counted in this state, because it specify Europe, North American on the Algerian Departments of France 2, on the territory of Turkey or on the Islands under the jurisdiction of any of the Parties in the North Atlantic area north of the Tropic of Cancer; Now, if Turkey is standalone covered, then one can argue Greek Island (next to turkey) should be too, which mean it really depends on how those island being interpreted, because if they are see as Greece Mainland, then they are in Europe, and Article 5 applies, but if they are see as outlyer, then article 5 MAY NOT applies because those island is not in North Atlantic Area north of the Tropic of Cancer.
On the other hand Article 7 lay out that if the issue is for the primary responsibility of the Security Council for the Maintenance of International Peace and Security, then Article 5 also would not applies. Which mean if Turkey have a case and argue all the way to UN and win its case, article 5 would also not applies if UNSC direct Turkey to recover those island.