Somalia has become the first country in the Horn of Africa to declare a locust infestation sweeping the region as a national emergency.

The country's Ministry of Agriculture said in a statement on Sunday the desert locust surge "poses a major threat to Somalia's fragile food security situation".

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"Food sources for people and their livestock are at risk," it added. "The desert swarms are uncommonly large and consume huge amounts of crops and forage."

The ministry said the emergency declaration was made to focus efforts and raise funds because it was critical to contain the locust swarms before harvests are due in April.

Desert locusts - whose destructive infestations cause large-scale crop damage and hunger - are a species of grasshopper that live largely solitary lives until a combination of conditions promote breeding and lead them to form massive swarms.

"Given the severity of this desert locust outbreak, we must commit our best efforts to protect the food security and livelihoods of Somali people," said Minister of Agriculture Said Hussein Iid.

"If we don't act now, we risk a severe food crisis that we cannot afford."

According to the regional Food Security and Nutrition Working Group, East Africa is already experiencing a high degree of food insecurity, with more than 19 million people facing acute hunger.

The locusts have led to what the Food and Agriculture Organization (FAO) has termed the "worst situation in 25 years" in the Horn of Africa.

The FAO says the current invasion is known as an "upsurge" - when an entire region is affected - however, if it gets worse and cannot be contained, more than a year or more, it would become what is known as a "plague" of locusts.

There have been six major desert locust plagues in the 1900s, the last of which was in 1987-89. The last significant surge was in 2003-05.