Finnish President Sauli Niinistö called his Turkish counterpart Recep Tayyip Erdogan on Saturday.
According to Niinistö's office, the two presidents discussed "Finland’s Nato membership, the security of the whole Euro-Atlantic region and the fight against terrorism".
In a subsequent tweet, Niinistö said that the two had had an "open and direct" conversation.
"I stated that as Nato Allies Finland and Turkey will commit to each other’s security and our relationship will thus grow stronger. Finland condemns terrorism in all its forms and manifestations," he tweeted, adding that the two leaders' "close dialogue" would continue.
Erdogan told Niinistö that "overlooking threatening terrorist organisations that pose a threat to a Nato member is not in the spirit of the alliance," Reuters reported.
Erdogan also said Ankara expected respect and support for its fight against terrorist organisations that threaten its national security and people, according to a statement by the Turkish presidency.
Last week the Turkish leader said that he would not approve the Nato applications filed by Finland and Sweden last week. He has accused Sweden in particular of supporting the Kurdistan Workers' Party (PKK), which the EU considers a terrorist organisation. Nato membership requires approval by all 30 existing members.
Ankara seeks end to arms embargo
Earlier on Saturday, Erdogan urged Swedish Prime Minister Magdalena Andersson to take "concrete steps" to end support for "terrorist" groups, his office said.
Erdogan told Andersson in a phone call that "Sweden's political, financial and weapon support to terrorist organisations must end," it said. He also said that an arms embargo against Turkey should be lifted.
Sweden and Finland imposed an arms embargo on Turkey in 2019 due to its incursion into northeast Syria. Erdogan said the move targeted a group it said was linked to the PKK.
According to the Anadolu news agency, Turkey expects "concrete steps" from Sweden over the PKK and other issues.
On Saturday evening, Erdogan told Nato Secretary General Jens Stoltenberg that Ankara will not look positively on Sweden and Finland's membership of the alliance unless they clearly show cooperation on the fight against terrorism and other issues.
"We agree that the security concerns of all Allies must be taken into account and talks need to continue to find a solution," Stoltenberg said in a tweet following the call.
Johnson: Concerns should be addressed before June summit
On Friday evening, British Prime Minister Boris Johnson told Erdogan that Finland and Sweden would be valuable additions to the alliance.
A spokesperson for Johnson said the PM also asked Erdogan on a call to work with Swedish, Finnish and Nato counterparts to address any concerns ahead of a leaders summit in Madrid in late June, and said the UK stands ready to support.
On Saturday morning, Speaker of Parliament Matti Vanhanen (Cen) told Yle that he was not worried about Finland's Nato membership application despite Turkey's threats to veto it.
The former PM said that Finland's accession to Nato will certainly be implemented, noting that some previous application processes have taken well over a year.
17.35: Updated with Erdogan, Johnson comments.
18.53: Updated with Stoltenberg comments.