Image copyright Marvel Comics Image caption The release of the first issue of X-Men Gold generated controversy in Indonesia

Marvel Comics has had to apologise and alter its latest comic release after one of its artists made hidden references to an ongoing political controversy in Indonesia.

The imagery included by Indonesian Muslim Ardian Syaf, a freelance contributor to Marvel, was called "bigoted" and he was accused of "spreading hatred" by social media users. Some even saw anti-Semitic sentiment in his artwork.

The first issue of Marvel's latest X-Men Gold series was released in early April. The entertainment giant has since said it will take the offending references out of subsequent print editions, as well as take disciplinary action.

The artist has also spoken to Indonesian media following the controversy, saying while he was expressing a political view, he was not trying to spread hate.

What are the references?

Image copyright Marvel Comics

Mr Syaf was able to get two politically-charged references into the comic.

The first reference was spotted on metallic Russian mutant Colossus, who wears an innocent-looking T-shirt during a baseball game.

The shirt has the words 'QS 5:51' on it - a reference to a passage in the Koran interpreted by some to mean that Muslims should not appoint Jews and Christians as their leader.

The number 51 also appeared elsewhere throughout the issue, further referencing the passage.

Image copyright AFP Image caption Mr Purnama is the first non-Muslim governor of Indonesia's capital Jakarta in 50 years

The reason this is controversial is because it is widely seen as a reference to the case against the governor of Jakarta, Basuki Tjahaja Purnama, widely known as Ahok.

Mr Purnama - a Christian of Chinese descent - is currently on trial for blasphemy.

He angered many hard-line Muslims after he referenced the passage while campaigning last year. The prosecution says he insulted Islam. Mr Purnama insists his comments were aimed at politicians "incorrectly" using the Koranic verse to make a case against his re-election.

If convicted, he faces a maximum five-year jail sentence.

The second reference came in a panel scene involving mutant and X-Men leader Kitty Pryde, who was seen addressing a crowd on the street.

The number "212" is written on a wall in this scene. Many readers noted its significance - the largest-ever street protest organised by hard-line Muslim demonstrators against Mr Purnama took place on 2 December (2-12) 2016. Mr Syaf had previously said that he participated in this rally.

Image copyright Marvel Comics Image caption In this panel, the numbers "212" referenced a significant political date in Jakarta

What is Marvel doing about it?

Marvel has since distanced itself from Mr Syaf's work and issued the following statement.

"The mentioned artwork was inserted without knowledge behind its reported meanings. These implied references do not reflect the views of the writer, editors or anyone else at Marvel and are in direct opposition of the inclusiveness of Marvel Comics and what the X-Men have stood for since their creation."

The X-Men are mutants who tackle bigotry as they fight for equality and peace with humans.

Illustrator Gary Choo, who has previously worked on Marvel artwork and covers, says sneaking political opinions and ideals into comics isn't something new.

"Politics should continue to find its way into comic books," he told the BBC. "But for what Marvel represents, this episode definitely did not fit into Marvel's storytelling."

Image copyright Marvel Comics Image caption The X-Men series touches on mutants who are persecuted by society

Why are people angry?

Mr Syaf has been responding to the outcry on his personal Facebook page saying those who were angry "did not know him".

"My career is over now. It's the consequence [of] what I did. Please, no more mockery, debate, no more hate. My apologies for all the noise. Good bye. May God bless you all," he said on Tuesday.

But that has not stopped angry reaction from Marvel fans and readers.

"No one needs to "know you" to understand what you did," wrote Andy Apsay on Facebook. "It was blatant and intentional. Swallow your pride. You are not bigger than Marvel."

Others like Gusti Made Sumariana said the artist was "spreading hatred towards Christians and Jews" with his work.

"Keep your bigotry out of the X-Men," wrote another Facebook user.

But the reaction has spiralled into a heated debate on the social media site, with supporters of Mr Syaf coming to his defence.

"People are free to react how they may. Artists are free to express what they do," wrote one user in Indonesian on Facebook.