Powerful bursts of hot ash and gravel have erupted twice from one of Indonesia's most active volcano, Mount Sinabung North Sumatra, on Friday, official said here. The eruptions belched the ash up to 1,500 meters high and the seismic activity of the volcano in Karo district remained high, diminishing hope for 17,094 evacuees in shelters to return home soon, Sutopo Purwo Nugroho, spokesman of national disaster management and mitigation agency told Xinhua over phone. Indonesia has been on red alert since the national volcanology agency has raised threat level of the volcano last month and extended evacuation zone to 5 km from 3 km earlier. Indonesia has issued a warning to international and domestic flights to reroute pathway near Mount. Sinabung since it erupted, with the biggest one on Nov. 18. The 2,475-meter high Mount Sinabung first rumbled back to life in September after being dormant for three years. The volcano has erupted intermittently since then. Indonesia, a vast archipelago country with 17,500 islands, is home to 129 active volcanoes and sits on a vulnerable quake-hit zone known as the "Pacific Ring of Fire."