A Turkish court imprisoned a convicted PKK terrorist a day after Sweden extradited him as part of a memorandum signed in June at a NATO summit to address Ankara's legitimate security concerns, paving the way for their eventual membership in the bloc.

Mahmut Tat was sentenced to more than six years in jail over being a member of the PKK terrorist group in Türkiye. He fled to Sweden in 2015, but Stockholm rejected his asylum request.

Tat arrived in Istanbul on Friday night after Sweden detained and extradited him, Anadolu Agency (AA) reported.

Turkish police arrested him soon after arriving at Istanbul Airport and referred him to a court on Saturday, which sent him to jail, the news agency said.

Finland and Sweden dropped decades of military non-alignment and sought to join NATO in May after Russia invaded Ukraine.

The decision requires a consensus within the U.S.-led defense alliance, but only Türkye and Hungary are yet to ratify their membership.

Foreign Minister Mevlüt Çavuşoğlu held trilateral talks with his Swedish and Finnish counterparts on the margins of a NATO meeting in Bucharest this week.

"The statements (coming out of Sweden) are good, the determination is good but we need to see concrete steps," Çavuşoğlu said.

Ankara has said it expects Stockholm to take action on issues including the extradition of criminals and freezing of terror assets.

Türkiye and the two Nordic countries signed a memorandum in June at a NATO summit to address Ankara's legitimate security concerns, paving the way for their eventual membership in the alliance.

Under the memorandum, Finland and Sweden extend their full support to Türkiye countering threats to its national security. To that effect, Helsinki and Stockholm are not to provide support to the PKK terrorist group's Syrian offshoots, the YPG, or the Gülenist Terror Group (FETÖ) – the group behind the attempted 2016 coup in Türkiye.

In its more than 40-year terror campaign against Türkiye, the PKK – listed as a terrorist organization by Türkiye, the United States, and European Union – has been responsible for the deaths of more than 40,000 people, including women, children and infants.

Turkish officials, including President Recep Tayyip Erdoğan, have warned that Türkiye will not give the nod to the memberships of Sweden and Finland until the memorandum is implemented.

Unanimous consent from all 30 existing allied countries is required for a country to join NATO.