UN Secretary-General Ban Ki-moon praised Iran on Thursday for releasing 12 political prisoners and seeking dialogue with the international community.

Ban, who is due to meet with President Hassan Rowhani next week, said he discussed Iran's nuclear program, the target of UN sanctions and the Syria conflict in talks with Iran's Foreign Minister Mohammad Javad Zarif.

"I told Minister Zarif that I commend the efforts of the new government in Iran in promoting dialogue with the international community," Ban told reporters.

"I also praised the government's actions in releasing 12 political prisoners yesterday, including the human rights lawyer, Ms Nasrin Sotoudeh, as well as a number of women's rights activists, political activists and journalists."

Recalling that he had demanded their release during a visit to Tehran in 2012, Ban said: "I am glad that they have finally taken action."

Ban said he told Zarif he was pleased Iran "is now taking some concrete steps to fulfil the promises made by President Rowhani during his recent election campaign."

Ban's spokesman Martin Nesirky said the secretary-general and Zarif discussed Iran's cooperation on its nuclear program and the role Tehran could play in promoting a political solution to the conflict in Syria.

Zarif told reporters he had a "good meeting" with the UN leader.

"We attach great importance to the role of the United Nations and we had a good discussion on the nuclear issues and on other issues," he added.

Western nations say Iran is seeking a nuclear bomb capability. Rowhani said in a television interview broadcast Wednesday that his country would "never" make a bomb.