A volcano overlooking Taiwan's capital Taipei is still active, and not dormant as long thought, potentially threatening an area that is home to three million people, local media reported Monday.

Datun Mountain, around an hour's drive from Taipei's city centre, could devastate the entire urban area if it were to erupt now, the China Post said, citing Academia Sinica, the island's main scientific institution.

The assessment is based on findings from the academy suggesting the volcano last erupted 5,000 years ago rather than 200,000 years ago, as previously thought, according to the report.

Scientists arrived at the revised date after analysing volcanic ash near the mountain. A final study is expected at the end of the year, the paper said.

An active volcano is defined as one that has erupted within the past 10,000 years, according to the Smithsonian Institution's Global Volcanism Programme.

Taipei Mayor Hau Lung-bin said he would consider the new findings and set up contingency plans for a possible eruption, according to the paper.

Academia Sinica was not immediately available for comment when contacted by AFP Monday.