Warner Bros global headquarters has apologised after its Japan office publicly complained that the US-based company was engaging with the “Barbenheimer” movement, which promotes a double bill of the apocalyptic Oppenheimer film and the lighthearted Barbie blockbuster.

There is a growing backlash in Japan against the conflation of Greta Gerwig’s playfully marketed movie with Oppenheimer, a biopic of the scientist behind the atomic bombs dropped on Hiroshima and Nagasaki.

The official US Twitter account for Barbie, a Warner Bros film, had this week replied to memes featuring atom bomb images and Barbie.

In response, a statement posted on Japan’s Twitter account for the Barbie film read: “Because the movies Barbie and Oppenheimer were both released in the US on 21 July, there is currently a movement driven by overseas fans to watch them together (#Barbenheimer), but this is not an official movement.

“We find the reaction to this fan-driven movement from the official US account for the movie Barbie to be extremely regrettable. We take this very seriously and are asking the US head office to take appropriate action. We apologise to those offended by these inconsiderate actions.”

On Tuesday, Warner Bros said in a statement it “regrets its recent insensitive social media engagement. The studio offers a sincere apology”.

The release of Barbie and Oppenheimer resulted in millions around the world seeing the two vastly different blockbusters as an ironic double bill dubbed “Barbenheimer”.

On social media, users have been sharing memes and art combining the fun pink imagery of Barbie with mushroom clouds and fiery explosions in Oppenheimer.

But the hashtag #NoBarbenheimer has been trending in Japan in the last week, with some social media users criticising the concept of Barbenheimer as trivialising nuclear weapons and the impact the bombings had on Japan, the only country to experience a nuclear attack. One #nobarbenheimer post, viewed 7m times, reads: “The official Barbie movie account is completely on board with the atomic bomb and mushroom cloud memes, so Barbie is a no-go as well.”

Warner Bros Japan’s statement came after the official US Twitter account for Barbie reacted positively to several Barbenheimer images shared by fans, including a fan-made poster depicting Oppenheimer actor Cillian Murphy carrying Barbie star Margot Robbie in front of a backdrop of flames. In response, the @barbiethemovie account wrote: “It’s going to be a summer to remember.”

Twitter later added a community note to the post highlighting the historical context of the image: “At 8:15 a.m. on August 6, 1945 (Showa 20), an atomic bomb was dropped on Hiroshima for the first time in human history. The particular nature of the damage caused by the atomic bombs is that mass destruction and mass murder occurred instantaneously and indiscriminately.”

Barbie is due to be released in Japan in August but Toho-Towa, Japan’s largest distributor of Hollywood films, has yet to announce a release date for Oppenheimer. Despite the sensitive subject matter, the country often shows foreign films depicting the events of the second world war without backlash. But Nolan’s film has been criticised by some for not showing the extent of the devastation wrought on Hiroshima and Nagasaki, where it is estimated up to 220,000 people died in the bombings and their aftermath.

Barbie has so far made $775m (£608m) globally and is already the third best-performing film of the year, while Oppenheimer, released by Universal Pictures, has made $400m, already more than Nolan’s previous film, Tenet.