The Observatory, which tracks the four-year-old Syrian civil war, said the attack also wounded 80 people and was carried out by Islamic State, a hard-line jihadist group which has fought Kurds in Syria and Iraq.
Nowruz is an important festival in Kurdish culture in which people gather to play games, dance and eat. In Syria, Nowruz is also celebrated as an expression of identity for the stateless Kurdish minority.
Syrian state television said the bombs exploded in the al-Mufti district of Hassaka.
Redur Xelil, a spokesman for the Kurdish YPG militant group which operates in northeastern Syria, also said Islamic State was responsible for the attack, which he said killed mostly women and children.
The YPG, which has emerged as the main ground partner for a U.S.-led coalition bombing Islamic State in Syria, has made significant gains in recent weeks in the north against the jihadists, cutting an important supply route from Iraq.
Over 200,000 people have been killed in Syria’s war, which started with peaceful pro-democracy demonstrations by many groups of society, including Kurds, and spiraled into civil war after protests were met with violence by the security forces.