Millions of locusts are swarming over southern Russia, destroying crops and forcing a state of emergency to be declared in the region.

The insects are eating their way through farmland in areas surrounding the eastern side of the Caspian Sea, the largest plague for 30 years according to local officials.

Over 800 hectares have been affected by the locusts, with officials claiming 10 percent of local crops have been destroyed, CNN reports .

"In Kalmikya, Astrakhan, Volgagrad and Dagestan, there is already no food left for the locusts, so they have moved on to other sources of food,” Tatiana Drishcheva from the Russia Agricultural Centre said.

Locusts descend on the area every year to breed.

It is believed that dry weather has helped speed the multiplication of the insects.