A statement from his spokesman said, "The secretary-general calls for the military junta to promptly complete the full transfer of power to civilian rule."
The statement said the arrests are "in contrast to other welcome developments that constitute important steps towards the full return of constitutional order" -- including the appointment of Dioncounda Traore as interim president and his decision to nominate Cheick Modibo Diarra as interim prime minister.
Members of Mali's armed forces took control of the country in March and announced the government then led by President Amadou Toumani Toure had been dissolved.
The military junta has since returned power to a civilian administration, with Traore replacing Capt. Amadou Sanogo, the leader of the group that seized power.
Government forces and Tuareg rebels in north Mali clashed in January, displacing numerous civilians from villages, and most of them have found refuge in other countries.
Meanwhile, Xinhua reported Mali's police chief announced Wednesday 11 civilians and 11 soldiers had been arrested.
Col. Diamou Keita, chief of Mali's National Gendarmerie, said the arrests resulted from an investigation that turned up weapons in homes that were not the type used by the army. He warned of a "new threat that is the infiltration of weapons in our country."