Singer-songwriter IU will release her new song "Night Letter," part of her upcoming fourth full-length album, this week, her agency said Monday.

The K-pop diva will release "Night Letter" on Friday, according to Loen-Fave Entertainment. The company released accompanying movie poster-like teaser images for the song on the artist's social media.

IU's new album will be released on April 21. The singer is scheduled to release another song on April 7 before the entire album comes out.

The upcoming, self-produced album is IU's first new material since "Chat-shire," an EP album that came out in October 2015.

"IU has collaborated with talented musicians," the agency said, and added that the work will bear IU's traditional sentimentality plus a new experimental sound.

The artist, who played the female lead in last year's TV series "Moon Lovers: Scarlet Heart Ryeo," most recently held a concert in Seoul in December.

Since making her debut in 2008, the 25-year-old has put out more than a dozen albums, including three full-length ones. (Yonhap)