“My heart goes out to the Jewish community around the world on this first day of Hannukah, a festival that celebrates the miracle of peace and light conquering darkness.” he wrote.
At least 11 people were killed when two gunmen opened fire on a Hanukkah celebration at Bondi Beach in Sydney, in what authorities have called a terrorist attack.
According to media reports, two of the victims were police officers. One of the attackers was killed and the other was arrested.
The Secretary-General was in Riyadh, Saudi Arabia, on Sunday, where he delivered a speech at the opening of the 11th World Forum of the United Nations Alliance of Civilizations (UNAOC).
The initiative was established 20 years ago to promote respect and understanding between cultures and religions.
Hannukah, also spelled Hanukkah, is the Jewish festival of lights.
It celebrates that the Jewish people regained the freedom to practice their religion more than 2,000 years ago in a battle against Seleucid (Syro-Greek) rule.
The eight-day celebration is celebrated by lighting candles each night in a holder called a menorah that is placed in interior windows or doors.