In the western province of Chimaltenango, landslides buried dozens of rural communities and killed at least 60 people, Erick de Leon, Chimaltenango's governor, said.
"There are a lot of dead people. The roads are blocked. The shelters are overflowing. We need water, food, clothes, and blankets," he said.
Tulio Nunez, the mayor of Santa Apolonia, a municipality in Chimaltenango, said he worried about the well-being of survivors in the area because landslides blocked roads and broke water pipes.
"They do not have anything to drink,'' he said.
In El Salvador, the death toll as a result of Agatha has risen to 10, two others have gone missing, and around 11,000 people were evacuated to shelters, Mauricio Funes, the country's president, said.
|Agatha triggered massive landslides that destroyed many homes and roads [AFP]
Gerson Martinez, the transportation minister, said about 95 per cent of roads were affected by landslides, but they remained open for public use.
He also said 179 bridges had been damaged.
Meanwhile, Jorge Melendez, the director of El Salvador's civil protection agency, said the Lempa River, which flows to the Pacific, overflowed its banks and flooded at least 20 villages.
Officials warned that the Acelhuate River, which cuts through San Salvador, the capital, has been running at dangerously high levels due to the storm and threatens to spill over into the city's streets.
Melendez said classes would be suspended on Tuesday in all primary and
secondary schools and public and private universities across El Salvador.
Flooding and landslides also destroyed 505 homes in Honduras, prompting authorities to evacuate 2,250 people.
Guatemala, El Salvador and Honduras have all declared state of emergencies to facilitate speedy deployment of government aid and resources.
Alvaro Colom, the president of Guatemala, had earlier said the government was considering putting the entire country under a state of emergency, extending one he declared on Friday in an area around the Pacaya volcano.
Hundreds of people were evacuated to shelters after the Pacaya erupted on Thursday, spewing ash that covered Guatemala City, the capital.
The volcano eruption killed at least one person, destroyed hundreds of homes and forced the closure of the capita's international airport.