A long dormant volcano has erupted in Eritrea, spewing a huge ash cloud across the Horn of Africa and threatening air travel.

The Volcanic Ash Advisory Center, which monitors volcanos for the aviation industry, says the Dubbi volcano began erupting late Sunday.

Germany's Lufthansa says it cancelled a flight out of the Eritrean capital, Asmara, and a flight into Addis Ababa from Frankfurt. The airline gave no reason for the flight cancellations.

U.S. officials said they had been told Ethiopia was considering shutting down Addis Ababa's main international airport due to the impending ash cloud.

Satellite images suggest Sudanese airspace could also be impacted.

The volcano, located in Eritrea's Red Sea region, last erupted in 1861.

The eruption follows a series of medium-sized earthquakes that struck the Eritrea and Ethiopia region on Sunday.

The U.S. Geological Survey says the biggest quake was magnitude 5.7.