Chinese netizens voiced anger Thursday over a Hong Kong advert portraying mainlanders as "locusts", sparking a call for calm in a state newspaper after an increasingly bitter exchange of words.

The advert was published in Hong Kong's widely-read Apple Daily Wednesday by an anonymous group in retaliation for comments made by Chinese professor Kong Qingdong, who called locals of the former British colony "dogs" and "bastards".

"How dare Hong Kong people have the courage to say we are locusts. No one should go to Hong Kong," said Reneeshou on Sina's popular microblog service.

"This shows a limited sense of appreciation (towards China) and a lack of tolerance of an international city," another commented.

The full-page advert demanded action to stop mainland Chinese "infiltration" of the territory, showing a huge locust overlooking Hong Kong's skyline with the words "Hong Kongers have had enough!" and "This city is dying, you know?"

Mainlanders are a key source of revenue for Hong Kong, but there is growing discontent over the thousands of mainland women who come to give birth in the territory every year, taking up limited beds and pushing up costs.

Many Hong Kongers also dislike the shadowy role that Beijing plays in local politics and the flashy displays of wealth by mainland Chinese tourists.

Mainlanders, for their part, complain people from Hong Kong -- which is part of China but enjoys more economic and political freedom -- look down on them.

Kong made the comments in an online, broadcast interview last week after a video of Hong Kongers scolding a mainland woman for disregarding rules and eating on a train went viral on the Internet.

"Originally, I didn't agree with Kong Qingdong, but after seeing the Apple Daily ad, I just want to say that these people really are mad dogs," one outraged web user wrote.

However, others admitted the behaviour of mainland Chinese travellers in Hong Kong could be improved.

"I do not like the Apple newspaper ad, but I think people who have been to Hong Kong should reflect on what they did. The quality of behaviour should be improved," another comment read.

The recent, barbed exchanges have prompted the official Global Times newspaper to call for calm.

In an editorial Thursday, the newspaper said China and Hong Kong should grow closer on the basis of a "shared identity".

"The mixed mutual feelings are making things more complicated. More efforts are needed from both the mainland and Hong Kong," it said.