Pop group BTS have recreated some of their classic photos as they kick off celebrations for their eighth birthday.

Every year, the Korean band mark the anniversary of their debut, 2 Cool 4 Skool, with "BTS Festa", a two-week event full of surprises for fans.

For 2021, that will include new videos, live performances and an online fan meet-up.

The celebration opened on 2 June, with the release of two dozen new group photos, known as "family portraits".

Eagle-eyed fans quickly spotted that some of the pictures looked familiar - with the seven-piece boyband re-staging classic poses from their past with more colourful outfits and backdrops this time around.

The celebration comes as the band's latest single Butter - a kinetic, Michael Jackson-inspired earworm - sets records around the world.

The song's music video was the biggest premiere in YouTube history, drawing in 3.9 million concurrent viewers for its premiere on 21 May.

It also set a new all-time record for YouTube video views in the first 24 hours, garnering over 108.2 million in the first day. On both occasions, the band were breaking records they already held - overtaking the success of last summer's hit single, Dynamite.

After the single dropped on Spotify, it was played 11,042,335 times in just one day, breaking the record for the most-streamed track on Spotify in the first 24 hours, beating Ed Sheeran and Justin Bieber's I Don't Care by 64,946 streams.

Butter went on to enter the UK charts at number three, and raced straight to number one in the US. It makes the band only the seventh act in history to earn their first four US number ones in less than a year, joining the likes of The Beatles, The Supremes, Paula Abdul and Mariah Carey, according to Billboard.

The BTS Festa is set to continue until 14 June, culminating in a live-stream concert and fan event, known as a "Muster".

Other notable events include new choreography videos on 4 June, BTS Room Live on 11 June and an event mysteriously titled as "Bicycle" on 7 June.

Fans have speculated that the last event will be a new single - or even a cover of Queen's Bicycle Race. BTS apparently discussed their love of the British rock band in a recent interview, with Jin saying: "Queen, please calls us."

Anniversary festivals are relatively common for K-pop acts, but more typically consist of a thank-you to fans in the form of a new video or special photos. The scale of BTS's event - which began in 2014 - is almost unheard of.