SEOUL, April 9 -- South Korean K-pop megastars BTS kick off their world tour on Thursday, riding the momentum of a chart-topping comeback album and a landmark performance in the heart of Seoul.

The seven-member group - widely regarded as the world's biggest boy band - took to the stage together for the first time last month following a years-long hiatus prompted by mandatory military service, and after releasing their latest studio album "ARIRANG".

The performance, on the doorstep of the historic Gyeongbokgung Palace, drew more than 100,000 fans to central Seoul, the group's label said, while its Netflix livestream attracted an estimated 18.4 million viewers worldwide, according to the streaming giant.

Spanning 85 shows in 34 cities wo...