The alert was raised after the agency recorded an increasing seismic activity around the 4,718-feet complex volcano in Kanagawa Prefecture. The mountain is located only 50 miles from the Japanese capital.
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The town of Hakone decided to restrict entry around the crater and closed the road to the mountain. The town is noted for numerous hot spring resorts, which attract scores of tourists. The operator of one of the most popular places in Hakone — Owakudani volcanic valley with hot springs — decided to suspend services in the area.
The previous alert for the volcano was issued in 2015, with the agency warning people not to approach the area. The latest eruption took place between the 12th and 13th centuries, according to scientists.