The four remaining members of the K-pop supergroup BTS are set to commence their 18-month military service in South Korea this week, joining three others who are already in service. Fans are now anticipating a prolonged hiatus for the group, with the likelihood of not seeing them perform together until 2025.

A group of fans braved rainy weather on Monday to bid a temporary farewell to the seven-member band's leader, RM and vocalist, V, in front of their boot camp in the central city of Nonsan.

"I think I'll be fine except for one thing, that I won't be able to make happy memories with you for a while, which is the hardest part," V wrote on fan platform Weverse on Monday, wishing fans well and happiness.

RM also wrote there that he might be lonely at times but that the 18 months would be a chance to get new inspiration and learn new things.

The duo were accompanied by other members of the band, including Jimin and Jung Kook, who will start their military service on Tuesday, and the three others who were given a day off from military duty, the Yonhap news agency said.

All able-bodied South Korean men ages 18-28 must serve in the military for about two years as part of efforts to guard against nuclear-armed North Korea.

Since announcing a break from group projects in June 2022, BTS members have pursued solo activities before starting military service.

Jin, 30, the oldest member, joined the army last December, followed by J-hope in April and Suga in August.

BTS' global success has triggered debate over whether K-pop artists should be allowed to serve for a shorter term, a perk granted to Olympics and Asian Games medallists and some classical musicians with international achievements.