Japan's Mount Aso erupted Wednesday, spewing a giant column of ash thousands of metres into the sky as hikers rushed away from the popular tourist spot.
No injuries were immediately reported after the late-morning eruption of the volcano in southwest Japan, which sent rocks flying in a dramatic blast captured by nearby CCTV cameras.
Authorities warned people not to approach the volcano as it ejected hot gas and ash as high as 3,500 metres (11,500 feet), and sent stones tumbling down its grassy slopes.
For those near the mountain, "caution must be exercised for large flying rocks and flows of pyroclastic materials", Japan Meteorological Agency official Tomoaki Ozaki told a televised press conference.
The last time the JMA set the same warning level for Aso was when it erupted in 2016, having rumbled to life the previous year after being dormant for 19 years.
The latest eruption came after a small one on Thursday, Kyodo News said.
Japan is one of the world's most volcanically active countries.
It sits on the so-called Pacific "Ring of Fire" where a large proportion of the planet's quakes and volcanic eruptions are recorded.
In September 2014, Japan suffered its deadliest eruption in almost 90 years when Mount Ontake, in central Nagano prefecture, burst unexpectedly to life, killing an estimated 63 people.