Saudi Arabia cleared 2,600 hectares of land of desert locust in the Eastern Province, the kingdom's Ministry of Agriculture and Water said on Monday.
Millions of locusts invaded farms and agricultural areas in Riyadh, Qassim, Hail and the Eastern Province in the past few weeks.
They pose a major threat to food security by feeding on plants and crops on farms.
The ministry said on Twitter that “43 field teams managed to treat 2,600 hectares of land for locusts by using 1,950 litres of pesticides in agricultural and border areas of the eastern region”.
Dammam and Hafr Al Batin were cleared of the insects, but swarms of locusts remain in Khobar, Qatif and Abqaiq, as well as the villages of Alia and Atfih. They are also on the Riyadh-Dammam highway and the Saudi-Kuwaiti border.
There are no locusts on the Saudi-Omani border, the ministry said.
Field teams are continuing to explore and follow up operations in all governorates.
The dense cloud of ravenous insects is also under control in Al Ahsa governorate in the Eastern Province, according to Saudi Arabia's state news agency.
Teams are on alert to deal with locusts and are fully equipped with pesticides, Ibrahim Al Kalil, director general of the ministry’s office in Al Ahsa, said.
"Farms in the governorate have not been damaged," Mr Al Kalil said.
Millions of locusts have swarmed in Saudi Arabia and Yemen over the past few weeks after countries in the Horn of Africa suffered the largest outbreak in decades.
Swarms of billions of locusts destroyed crops in Kenya, which had its biggest outbreak in 70 years, as well as Somalia and Ethiopia, which have not faced swarms that size in 25 years.
The UN warned “we simply cannot afford another major shock” to an already vulnerable African region.