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Walt Disney Japan has apologized for a tweet expressing congratulations on the 70th anniversary of the atomic bombing of Nagasaki.

A post on Disney Japan’s corporate account on Sunday featured a picture of Alice from the animated movie “Alice in Wonderland" and a line from one of the movie’s songs in English: "A very merry unbirthday to you."

The text in the tweet, in Japanese, translated roughly to "congratulations on a not special day."

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Twitter users quickly expressed outrage, many in Japanese and some in English and other languages.

#Disney 's unbirthday tweet was inappropriate in August 9 Nagasaki Atomic bomb 70 years anniversary. — ナゴサング (@nago_sang) August 9, 2015

The Disney Japan tweet was deleted but was shared widely online.

Disney Japan on Monday posted a tweet offering "deep apologies" for having caused discomfort. The tweet said social media managers would be more careful in the future.

The Walt Disney Co. operates more than 1,000 social media accounts, according to its website.

A longer statement on Disney Japan's website blamed the poorly timed tweet on "insufficient note of the day of dispatch."

More than 74,000 people were killed in the American bombing of Nagasaki, three days after the bombing of Hiroshima. Japanese citizens mark the anniversaries with solemn ceremonies.