Ecuador issued an orange alert -- the second-highest warning level -- for towns near the Tungurahua volcano on Sunday, as its level of activity rose, civil defense officials said.

The area of the warning covers the adjacent provinces of Tungurahua and Chimborazo, according to the national civil defense agency.

Greater activity has been building since Wednesday, along with a slight increase in gas emissions from the 5,029-meter (16,500-foot) volcano, located about 135 kilometers (84 miles) south of the capital Quito, the Geophysical Institute said.

Eruptions at Tungurahua, which means "Throat of Fire" in the indigenous Quechua language, peaked in 2006, killing six people in a Chimborazo village.

Several communities near Tungurahua, including the tourist town of Banos with 15,000 people, also were forced to evacuate during the volcano's violent eruption in 1999. Residents could only return to their homes a year later.