UN Secretary-General Antonio Guterres said he is closely monitoring developments in the latest tragedy in Haiti, while the UN Children's Fund said its teams are already on the ground making assessments to prioritise urgent needs and provide assistance to affected populations following the 7.2-magnitude quake, which reportedly killed more than 200 people.
"My heart goes out to all those affected by the earthquake. My deepest condolences to all those who have lost family and friends," António Guterres said on Twitter.
Many children and their families are feared to have fled their homes.
In a statement, UNICEF said the quake was felt in the Haitian capital, Port-au-Prince, but the epicentre was detected in the south of the country.
Severe damage, injuries and casualties have been reported in the departments of Grande Anse, Sud and Sud-Est.
According to reports from the region, the latest earthquake, similar in magnitude to the 2010 quake that devastated the country and left hundreds of thousands dead and displaced, has toppled churches and schools, and severely cut off electricity in the affected areas.
"We are deeply saddened by the reports of casualties and severe damage following today's earthquake in Haiti," said UNICEF Representative in Haiti Bruno Maes, adding that UNICEF stands in solidarity with families and children in the aftermath of the disaster.
Bruno Maes noted that UNICEF is working with the government and other non-governmental actors to provide support to affected communities, and warned that children and families are feared to have been forced to flee their homes as a result of the earthquake and may be in urgent need of shelter, clean water, medical care and protection.
Henrietta Fore, head of the UN agency, reiterated on Twitter that she was deeply saddened by the tragedy unfolding: "Today and in the coming days, UNICEF will be working closely with our partners to reach affected children and families".
The earthquake has come as a tropical storm bears down on the Caribbean region and as Haiti itself faces a recent surge in cases of COVID-19 as it continues to deal with the socio-political fallout from the assassination of its President Jovenel Moise last month.
"Our thoughts are with the people of Haiti in the aftermath of the devastating earthquake," said UN Deputy Secretary-General Amina Mohammed in a Twitter message, in which she also stressed that the organisation "pledges to deliver in solidarity".
For his part, Collen Vixen Kelapile, president of the UN Economic and Social Council, said that "the people of Haiti are in our thoughts at this difficult time".
Kelapile added that the Council's Ad Hoc Advisory Group on Haiti will continue to work to promote the long-term development of the country, referring to the body created to advise and promote the socio-economic recovery, reconstruction and stability of the country.