A small group of desert locusts has entered Congo, marking the first time the voracious insects have been seen in the Central African country since 1944, the UN Food and Agriculture Agency said Tuesday as UN agencies warned of a "major hunger threat" in East Africa from the flying pests.

Kenya, Somalia and Uganda have been battling the swarms in the worst locust outbreak that parts of East Africa have seen in 70 years. The UN said swarms have also been sighted in Djibouti, Eritrea and Tanzania and recently reached South Sudan, a country where roughly half the population already faces hunger after years of civil war.

A joint statement Tuesday from FAO director-general Qu Dongyu, UN humanitarian chief Mark Lowcock, and World Food Program (WFP) Executive Director David Beasley called the swarms of locusts "a scourge of biblical proportions" and "a graphic and shocking reminder of this region's vulnerability."

The FAO said mature locusts, carried in part by the wind, arrived on the western shore of Lake Albert in eastern Congo on Friday near the town of Bunia. The country has not seen locusts for 75 years, it said.

"Needless to say the potential impact of locusts on a country still grappling with complex conflict, Ebola and measles outbreaks, high levels of displacement, and chronic food insecurity would be devastating," the UN officials said in the joint statement.

Locust swarms can reach the size of major cities and can destroy crops and devastate pasture for animals.

Experts have warned that the outbreak is affecting millions of already vulnerable people across the region.

Uganda's government said Tuesday it was trying to contain a large swarm and will need more resources to control the infestation that has spread to over 20 districts in the north. Soldiers have been battling swarms using hand-held spray pumps, while experts have said aerial spraying is the only effective control.

The UN recently raised its aid appeal from 76 million U.S. dollars to 138 million U.S. dollars, saying the need for more help is urgent.

"This funding will ensure that activities to control the locusts can take place before new swarms emerge," the UN officials said, noting that to date only 33 million U.S. dollars has been received or committed.

Experts have warned that the number of locusts if unchecked could grow 500 times by June, when drier weather is expected in the region.

"WFP has estimated the cost of responding to the impact of locusts on food security alone to be at least 15 times higher than the cost of preventing the spread now," the UN officials said in the statement.

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A changing climate has contributed to this outbreak as a warming Indian Ocean means more powerful tropical cyclones hitting the region. A cyclone late last year in Somalia brought heavy rains that fed fresh vegetation to fuel the locusts that were carried in by the wind from the Arabian Peninsula.

Desert locusts have a reproduction cycle of three months, the UN officials said, and mature swarms are laying eggs in vast areas of Ethiopia, Kenya and Somalia, "many of which are already hatching."

"In just a few weeks, the next generation of the pests will transition from their juvenile stage and take wing in a renewed frenzy of destructive swarm activity," the joint statement said.

This is a time when farmers' crops begin to sprout, which could devastate East Africa's most important crop of the year, the UN officials said.

"But that doesn't have to happen," they said. "The window of opportunity is still open. The time to act is now."