Tatyana Kotenko, of the hydro-meteorological station Severokurilsk, said steam and gas clouds could be seen rising some 150 meters (450 feet) above the Ebeko volcano's crater in the morning.
"The volcano is spewing out steam and gases 100 to 300 meters (300 to 900 feet) [into the air], with the temperature upwards 100 degrees Celsius (212 degrees Fahrenheit)," Kotenko said.
"With a western wind blowing, or when there is no wind, Severokurilsk residents can smell the sulfur and chlorine."
The 1,138-meter (3,300-foot) Ebeko volcano has three summit craters, each 350 meters (1,000 feet) in diameter. Its historical activity, recorded since the late 18th century, has so far been restricted to small-to-moderate explosive eruptions from the craters.