Image copyright Paramount Pictures Image caption Shanghai's Oriental Pearl Tower (bottom right) was added to the Hong Kong skyline

It probably was not the publicity they were hoping for.

Earlier this week, Paramount Pictures released a series of posters to promote upcoming sci-fi film Arrival.

One poster showed a UFO hovering above Hong Kong's iconic skyline - except the skyline also included Shanghai's Oriental Pearl Tower.

The blunder enraged many Hong Kong social media users, who flooded the film's Facebook page with the hashtag #HongKongisnotChina.

Hong Kong, a former British colony, was returned to Chinese sovereignty in 1997.

But it is deeply divided over its relationship with China, and many in the territory have a strong sense of Hong Kong identity.

Hong Kong's democracy debate

One comment on the film's Facebook page said: "Please improve on the accuracy of your posters, the Shanghai tower does not belong to Hong Kong, remove that please. Please don't mix up Shanghai and Hong Kong. They are totally different, it's very offensive to a lot of people from Hong Kong."

"Hong Kongers are now feeling insulted and offended," said another.

Some went as far as to call for a ban on the film, which stars Amy Adams and is set for release in November.

'Glass hearts'

The poster was later removed from the Facebook page and a statement was posted saying: "An error in one in a series of posters for 'Arrival' was made by a third party vendor."

"We are disappointed to have not caught the error."

Later a similar poster with the actual Shanghai skyline appeared.

Image copyright Paramount Pictures

Not everyone was pleased, though, with the fact Hong Kong's skyline had now been replaced with Shanghai's.

"The appearance of the Oriental Pearl Tower in HK was wrong, so you rectified it by keep the tower and replacing the city of HK with Shanghai? So HK's the "WRONG" part here?" Facebook user Jonathan Ip wrote.

Meanwhile, some people have made fun of the commenters, accusing them of overreacting, or having "glass hearts" - a Chinese phrase referring to fragile egos.

What are Hong Kong's localists angry about?

Hong Kong was handed over to China by Britain in 1997, under an agreement that certain rights and freedoms would be guaranteed for 50 years.

As a result, Hong Kong has its own legal system, and enjoys rights including freedom of assembly and free speech, which are restricted in mainland China.

However, there are growing concerns over what is seen as interference by Beijing into Hong Kong affairs.

In 2014 there were mass demonstrations demanding full democracy in Hong Kong, after the Chinese government said it would allow the territory to elect its leader - but only from a pool of Beijing approved candidates.

After that movement failed to win any concessions from Beijing, there has been an increase in localist sentiment, with some people demanding greater autonomy for Hong Kong, and protection against what they see as the dilution of the city's identity.