Turkey and Hungary are the only NATO members yet to ratify Sweden's membership request, which came after Stockholm dropped its long-standing policy of non-alignment last year after Russia launched its war on Ukraine.

Erdogan agreed at a NATO summit in Vilnius in July to put the ratification of Sweden's membership before the Turkish parliament as pressure grew on Ankara from partners.

"Sweden's NATO membership protocol was signed on October 23, 2023, by President Recep Tayyip Erdogan and sent to the Grand National Assembly of Turkey," the presidency posted on X, formerly Twitter.

Swedish Prime Minister Ulf Kristersson called the announcement "encouraging news".

"Now it remains for the parliament to deal with the issue," Kristersson said, also in a post on X.

"We look forward to becoming a NATO member," he added.

NATO chief Jens Stoltenberg on Monday urged a quick vote by Turkey's parliament to approve Sweden's membership.

"I welcome President Erdogan's signature of the accession protocol for Sweden and its referral to the Grand National Assembly. I look forward to a speedy vote to ratify, and to welcoming Sweden as a full NATO ally very soon," he said in a statement.

Sweden's Nordic neighbour Finland, which applied to join NATO at the same time, was granted membership in April.

Erdogan has put pressure on Sweden to take measures over Koran burnings at protests in the country that have angered many in Muslim countries.

Ankara also says Sweden is harbouring outlawed Kurdish militants, and has demanded their extradition.