Both sides said earlier they would observe the truce starting at 3am local time, or 9am Hong Kong time.
Soon after the appointed time, Russia’s defence ministry said it had suspended strikes on the region.
The war-ravaged city in Ukraine’s southern Kherson region has been caught in the crosshairs of fighting between the two sides since 2022, when it was seized by Russian forces at the start of their invasion.
Former residents said earlier this year that those remaining in the city were starving, lacked medicine and could not easily leave.
The ceasefire, which applies to a limited area, comes as the Ukraine war grinds through its fifth year.
Three-way peace talks between Washington, Moscow and Kyiv are set to resume in November after a months-long hiatus.
Neither Russia, Ukraine nor the United States has said who would monitor the truce, or given details about the humanitarian operation set to accompany it.
Announcing last Friday that she had brokered the ceasefire, Melania Trump said civilian officials from both Russia and Ukraine would visit residents in their homes and “determine the level of assistance they require”.
Neither Russia nor Ukraine has said how long the truce would last.
The Russian defence ministry said on Friday it would halt fire in the “Kherson sector” for the duration of the ceasefire, without giving details.
The city, on the southern bank of the Dnipro River, has seen its population drop from about 24,000 before the conflict to around 2,000.
Those remaining include up to 50 children, according to Ukrainian and US estimates.
Former residents told AFP earlier this year that people still living in the city were forced to hunt pigeons or survive on whatever they had in their garden.
The city was heavily damaged by the 2023 destruction of the Kakhovka dam, which unleashed major flooding along the Dnipro River. (AFP)