K-pop sensation BTS are celebrating their 10th anniversary and band members RM, Jin and Jimin have written special letters to their fans.

BTS or Bangtan Sonyeondan debuted a decade ago with the single album '2 Cool 4 Skool', which was released on June 12, 2013. The septet also includes Suga, J-Hope, V and Jungkook.

Jin, whose full name is Kim Seok-jin, posted the letter for BTS ARMY, as the bands fans are known across the globe, on fan community forum Weverse.

The 30-year-old vocalist, who enlisted for military duty in December last year, said he was sad that he could not celebrate the band's milestone moment with the fans.

"I should have filmed more contents before I joined the army.. I don't know how to express my apologies. As far as I know, the remaining members are working hard on the 10th anniversary contents," he wrote. Group leader RM, whose real name is Kim Namjoon, said the group shares a special bond with their fans who helped them become popular worldwide.

"The concerns and ambivalence that I had at 17 and 20 are still valid. As I grow up, there are so many things in the world that words and writings alone cannot explain. And I learned that things that didn't seem to change will change someday," the 28-year-old said.

In his letter to the fans, Jimin, 27, thanked them for their constant love over the past 10 years.

"I’ve told you ARMYs a few times already, it’s not easy to support and love someone and give them strength for no particular reason. That is why I am able to understand how happy we are.

"You, who made us feel this way, should feel overflowing happiness and receive love. You must. Understand? ARMY, whom I am always thankful to and love, Let’s be happy for a long long time," the singer, whose real name is Park Ji-min, said.

V, whose real name is Kim Tae-hyung, shared behind the scenes footage of the band on social media to celebrate the anniversary with fans.

Meanwhile, BigHit Music, the management agency of BTS, released the digital single "Take Two" to mark the 10th anniversary of the music group.

The group -- known for hit songs such as "Blood Sweat Tears", "Boy in Luv", "ON", and "Dynamite" -- announced their hiatus last June and the members hope to reconvene as a unit around 2025 following their service commitment.

BTS anniversary is a massive pop culture event in South Korea with the country planning a series of events to celebrate the band that has been credited with putting their culture and music on the global map.

From Monday, all the landmarks in Seoul such as the City Hall, Han River bridges and Lotte World Tower have been lit up in purple, the band's colour, to celebrate the 10 year anniversary of the group's debut. Postal authorities have issued stamps to commemorate the anniversary which marks the beginning of a week long celebration in the country and amongst BTS global fans.

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