BANOS, Ecuador (AFP) -- A volcano in southern Ecuador erupted Thursday, burying five villages in lava and ash and leaving at least five people dead, 13 injured and dozens missing, local authorities said.

President Alfredo Palacio declared a state of emergency in the four affected provinces before heading to Penipe, at the foot of the active Tunguraua volcano, accompanied by several ministers.

The sky around Tunguraua, located 135 kilometers (83 miles) south of Quito, was thick with ash, blocking access by helicopter or plane.

About 3,200 people were evacuated and more than 20,000 hectares (50,000 acres) of farmland were destroyed, said Penipe Mayor Juan Salazar, whose town was among the worst hit.

"Red-hot lava and ash buried five villages, killing five persons," Salazar told AFP by telephone. "Four of the bodies cannot be recovered because they are buried under the debris," he said. "Everything was knocked down. In one of the settlements, lava set fire to 12 houses that are still burning."

Tunguraua erupted violently before dawn, following a 4.4-magnitude earthquake that struck Wednesday southeast of the volcano.

Airports announced closures in nearby Riobamba, Latatunga and Guayaquil, Ecuador's most-populous city, due to airborne ash.

Unable to fly due to the smoke, the president traveled to Penipe by land, Palacio's office said.

"The situation is indescribable. There are approximately 60 people missing in the highest-risk area, as well as seven injured people who were taken to the city of Riobamba and six others injured in Penipe," Salazar told television network Ecuavisa.

The mayor said the 5,029-meter (16,500-foot) volcano disgorged lava and flames. "A very powerful explosion this morning produced glowing rocks, ash and lava that devastated several areas," Salazar said. "We suffered 18 continuous hours of fire."

"We need helicopters to search for people we could not rescue at night," Salazar said. He added that things could get worse if the Puela and Chimbo rivers are blocked.

One resident said the area around the volcanic cone was covered with a dense layer of ash, about five centimeters (two inches) thick.

"Penipe is in the dark, as if it were night. There is a lot of ash. Rocks drove holes in the houses. I saw a lot of injured people," the resident told a radio station.

"Approximately 1,500 people who had been evacuated (after a July 14 eruption) had to leave their homes again in the villages of Cusua, Bilbao and Juiva, due to increased activity in the volcano," said Mauro Rodriguez, a retired army colonel in charge of the evacuation.

The eruption is the strongest since 1999, bigger than the one on July 14 that destroyed 20,000 hectares (50,000 acres) of farmland and left 10,000 people homeless, Quito University's Geophysical Institute said.

"We can't say whether this is the last eruption," said institute director Hugo Yepez.

"We have to watch the volcano, but we can say that the calm after the explosions could last weeks or days," he said.

Institute vulcanologists pinpointed the strongest eruption near midnight Wednesday and said it lasted until 3:00 am (0800 GMT) Thursday.

The quake struck Wednesday at 12:16 am (0516 GMT), according to the US Geological Survey, which described the magnitude 4.4 quake as "light," 180 kilometers (110 miles) southeast of Quito at a depth of 32.6 kilometers (20.3 miles).