The Anak Krakatau volcano in Indonesia erupted overnight, sending fiery smoke 500m into the air, the country's volcanology agency said on Saturday.
The alert level of the volcano, located between the islands of Java and Sumatra, remained at the third-highest level, said the Centre for Volcanology and Geological Hazard Mitigation.
Anak Krakatau triggered a tsunami during an eruption in December 2018, which killed more than 430 people.
Thousands were injured.
The 2018 eruption caused the volcano to lose much of its visible height.
The Anak Krakatau island was created after the legendary eruption of the Krakatau volcano in August 1883.
The eruption was so violent that the volcanic island that had existed until then sank into the sea.
More than 35,000 people lost their lives.
The sea between Sumatra and Java, like the rest of the island nation, sits on the Pacific Ring of Fire, the most geologically active zone on earth where volcanic eruptions and earthquakes are frequent.