Sprinkling a sugary coating of teen-idol pop on to the remorseless clamour of death metal sounds like a musical fusion best confined to the imagination of a record industry executive.

But Babymetal, a trio of Japanese teenage girls, have paired rah-rah skirts and hair ribbons with infernal metallic riffs to produce what could be the most unlikely music phenomenon of the year.

The band's eponymous debut album is No 3 on iTunes' US rock chart and has made the online top 10 in six other countries, including the UK. The video for their new single, Gimme Chocolate, has received more than 3.7m views on YouTube, and their dramatic arrival on the international metal scene won them a place on the cover of the latest edition of Kerrang! magazine.

Babymetal's music owes more to the uncomfortable marriage between the J-pop perennials of Lolita fantasy than to the bare-bones metal sound of, say, Slipknot. In the Gimme Chocolate video, the guitarists and drummer are practically invisible, while the catchy chorus will sound more familiar to fans of J-pop girlband AKB48.

Babymetal – Suzuka Nakamoto, 16, Moa Kikuchi and Yui Mizuno, both 14 – grew out of the all-girl band Sakura Gakuin. Their mission – to fuse the saccharine sound of J-pop with thrash metal – was daunting, given none of the girls had even heard of metal before being thrown together by executives at the Amuse talent agency. But they have handled their tricky musical brief with ease.

The band's first major single, Ijime, Dame, Zettai, sold 19,000 copies in its first week and debuted at number six in the Japanese Orion weekly singles chart.

Steve McClure, the executive director of the online music site McClure Music, described "karaoke-friendly" Gimme Chocolate as "well done for what it is".

"Babymetal have some clever marketing and slick production values behind them. They're a good example of a spin on the 'kawaii' [cute] template. The song is a bit formulaic in the sense that it's a knock-off of the AKB48 kawaii genre, but it's a catchy tune."

Despite the phenomenal domestic success of AKB48 and other girl bands, J-pop has struggled to make an impact outside north-east Asia. Korea's Girls' Generation and Co, however, is riding a global K-pop wave.

And yet McClure does not forsee Babymetal as the new face of Japan's pop industry. The critic has drawn an unfavourable comparison between the band and rival outfit Kyary Pamyu Pamyu, whose viral success led to a sellout concert at the Japan Expo in Paris in 2012 and a world tour the following year.

"I see them more as a novelty act, and by definition that means they're probably going to be a one-off," he said. "And Babymetal aren't really being marketed as a Japanese act. They're coming out of leftfield, so I'm sceptical about this being the start of something bigger for J-pop."

Just as South Koreans had been listening to Psy for years before he became a household name with Gangnam Style in the summer of 2012, Babymetal are hardly new – they formed three years ago – and have since appeared on Japan's festival circuit, performing twice at Summer Sonic in Tokyo and Osaka.

At the end of last year, they performed overseas for the first time, in Singapore, on the back of their Death Match tour of Japan. Earlier this month, they became the youngest band to play Tokyo's revered Budokan arena.