"They are suspected of being affiliated with the Islamic State and were planning an attack on the New Year in Ankara," the official said, asking not to be named.
Counter-terror police arrested the two people in the Mamak district in the outskirts of the capital, the private NTV television reported.
Turkey is on high security alert after 103 people were killed on October 10 when two suicide bombers ripped through a crowd of peace activists in Ankara, the worst attack in modern Turkey's history.
Turkish authorities have over the past months cracked down on the group's so-called "sleeper cells" throughout the country.