MADRID (Reuters) - An ISIS fighter has become the unlikely target of Spanish social media ridicule after threatening Spain that more attacks will follow the assaults in Catalonia that killed 15 people.

Twitter users responded to an Islamic State in Iraq and Syria (ISIS) video, released on Wednesday (Aug 23), by turning the young Spanish-speaking extremist into a meme that was among the social media site's most popular trending topics on Thursday and Friday.

In one, the bearded extremist becomes a YouTube blogger asking viewers to like, and subscribe to, his channel. In another, he raps along to a reggaeton track dubbed the "official ISIS remix".

"When you see me, I know you're trembling," the fighter raps in a version of Puerto Rican rapper Bad Bunny's hit Tu No Metes Cabra (You Don't Scare Me).

In the original video, the fighter said ISIS would avenge Muslims killed in the 15th-century Spanish Inquisition and rebuild Al Andalus, the mediaeval Muslim territory that occupied most of modern Spain and Portugal.

ISIS claimed responsibility for the attacks on Aug 17 and 18, in which militants in a van mowed crowds down on Barcelona's most famous avenue and then later assaulted the Catalan seaside resort of Cambrils.

Spanish media, citing police sources, has identified the fighter as 22-year-old Muhammad Yasin Ahram Perez, born in the southern Spanish city of Cordoba, who moved to Syria to join ISIS in 2014 with his mother and brothers.

One popular meme with the fighter, known as El Cordobes, referred to a Spanish online backlash last year against British chef Jamie Oliver for attempting to remake the classic Spanish rice dish, paella, by adding mussels and chorizo.

"An authentic paella is made WITHOUT seafood," the fighter is quoted saying in the tweet's caption.