"Sweden has taken significant concrete steps to meet Turkey's concerns," Stoltenberg told reporters after meeting President Recep Tayyip Erdogan. "Sweden has fulfilled its obligations."

Stoltenberg attended on Saturday the inauguration of Erdogan, who was re-elected to serve another five years, in a lavish ceremony joined by dozens of world leaders in the capital Ankara.

NATO member Turkey has dragged its feet over admitting Sweden to the military alliance. It and Hungary are the only two member countries yet to ratify the membership bid.

Finland formally joined the alliance in April.

Erdogan has accused Sweden of being a haven for "terrorists", especially members of the Kurdistan Workers' Party (PKK), a group blacklisted by Turkey and its Western allies.