Mount Lokon spews hot lava and volcanic ash during an eruption in Tomohon in Indonesia's North Sulawesi province July 14, 2011. [Photo/Agencies]

JAKARTA - Indonesian transport ministry has warned planes to avoid flight routes near a volcano, which has been erupted, in North Sulawesi, a senior official told Xinhua Friday.

Mount Lokon re-erupted at midnight Thursday, spewing volcanic ash up to 2,000 high, and after midnight Friday, spewing ash by up to 700 meters high.

"We have issued a warning for planes passing the area not to pass the routes near the volcano for their safety," Director General for Air Transport Herry Bhakti Gumay told Xinhua.

So far, the eruption has not impacted either national or international routes, all airports in North Sulawesi still operate, but the authorities keeps monitoring the condition of air quality around the airports, as the volcano seismic activity is still high, according to Bhakti.

"Airports have been informed to be alert," he said.

International flight route had been disturbed when Mount Merapi in Yogyakarta of Java Island erupted last year. The volcano ash forced President Barack Obama cancelled his visit to the world's biggest temple of Borobudur in Yogyakarta for fear that volcanic ash damaging plane engine.

Mount Lokon has been on top alert since Sunday and there is still no signs of decreasing seismic activity.

As many as 129 active volcanoes lie in Indonesia which sit on a vulnerable quake-hit zone so called the "Pacific Ring of Fire", where two continental plates meet that frequently cause seismic and volcanic movements.