UN Secretary General Antonio Guterres arrived at a time of urgent need to address an outbreak of cholera and severe drought ravaging the Horn of Africa nation.
Guterres, who flew in here from Nairobi, called for a global response to stop deaths in Somalia and noted that people were dying of hunger and cholera, Xinhua news agency reported.
"Just arrived in Somalia on emergency visit to focus on famine and cholera. People are dying. The world must act now to stop this," he tweeted.
Guterres, who was due to hold talks with newly-elected President Mohamed Abdullahi Mohamed, said the current drought in Somalia required a "massive international response".
The UN announced last month that Somalia was slipping into famine six years after a deadly one which claimed more than 250,000 lives.
The UN chief is expected to meet the country's leadership and members of the international community to bolster efforts against the drought.
Humanitarian agencies have called for international help warning that urgent steps must be taken to prevent the country from falling into famine even as the new administration takes over office.
The UN also confirmed on Monday that 196 people have died from acute watery diarrhoea (AWD) and cholera outbreak in Somalia since January.