Visiting UN Secretary-General Antonio Guterres appealed Tuesday for "massive" international support for Somalia as it battles a devastating drought and a grinding Islamist insurgency.

Guterres, who arrived in Somalia's capital Mogadishu earlier on Tuesday, described his trip as a visit of "solidarity."

"I am also here to ring the alarm on the need of massive international support," he said, pointing to the difficulties faced by the country as it grapples with climate disasters and militancy.

"Although Somalis make no contribution to climate change, the Somalis are among the greatest victims. Nearly five million people are experiencing high levels of acute food insecurity," he said.

Somalia 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 against the Al-Qaeda linked Al-Shabaab Islamist militant group.

The United Nations has launched a $2.6-billion appeal for humanitarian aid for the troubled Horn of Africa nation, but Guterres said it is currently only 15 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 UN says about half its population will need humanitarian assistance this year, with 8.3 million affected by the drought.

Somalia was hit by a famine in 2011 which killed 260,000 people, more than half of them children under six, partly because the international community did not act fast enough, according to the UN.

President Hassan Sheikh Mohamud last year declared "all-out war" against Al-Shabaab, which has been fighting the fragile central government for more than 15 years.