Antonio Guterres made the remarks during a telephone conversation with Foreign Minister Abbas Araghchi on Friday.
The UN chief stressed the need to prevent the escalation of tensions and to reduce their humanitarian and security consequences in the region.
The comments came more than three weeks into the unlawful attacks that have targeted Iran's military and civilian infrastructures alike, leading to the martyrdom of numerous people, including the Leader of the Islamic Revolution Ayatollah Seyyed Ali Khamenei and senior commanders as well as hundreds of women and children.
According to Iran's Red Crescent Society, the atrocities have damaged more than 70,000 civilian targets such as residential areas, business centers, schools, and vital infrastructures.
The Islamic Republic has retaliated by targeting sensitive and strategic Israeli and American assets throughout the region, including those lying in the regional countries cooperating with the aggressors.
Tehran has underlined its right to reprisal in line with international law, while urging states across the region to prevent their respective territories from being used as launch pads for attacks on Iranian soil.