UN Secretary-General Antonio Guterres attends a meeting. File photo

Pictures on social media showed Guterres being given a red carpet welcome at the capital city's airport by Somalia's Foreign Minister Abshir Omar Huruse and other leaders.

Somalia has imposed a security lockdown on Mogadishu for the unannounced visit, with most roads closed, and public transport restricted.

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Guterres's arrival comes as the country is in the grip of a calamitous drought that has driven many to the brink of famine, while the government is also engaged in a major offensive to put down a bloody Islamist insurgency.

The UN has launched a $2.6 billion appeal for humanitarian aid for the troubled Horn of Africa nation, but it is currently only 13 percent funded.

Five straight failed rainy seasons in parts of Somalia as well as Kenya and Ethiopia have led to the worst drought in four decades, wiping out livestock and crops and forcing at least 1.7 million people from their homes in search of food and water.

While famine thresholds have not been reached in Somalia, the United Nations says about half its population will need humanitarian assistance this year, with 8.3 million affected by the drought.

"The crisis is far from over — needs remain high and urgent," the UN's resident coordinator for Somalia, Adam Abdelmoula, said last week in Geneva.

"Some of the most affected areas continue to face the risk of famine."

Agence France-Presse