Image copyright Getty Images Image caption Whale sharks are gentle fishes that feed on micro organisms

Two fishermen have been detained in China over the killing of a whale shark days after one found fame online.

Pictures of a huge fish had been posted online by workers on an oil rig near Weizhou Island, south of Guangxi province, in early May.

It soon attracted much admiration on China's Twitter-like social media platform Sina Weibo.

Then two days later, news spread that a whale shark had been killed and sold as fish food at nearby Beihai market.

Photos circulated online showed a huge whale shark being winched onto a pier by crane.

Image copyright Sina Weibo / CNOOC WZ11-4 Platform Image caption Workers on board the Weizhou 11-4 oil rig says the sharks return every May

Beihai police have confirmed the fish sold at the market was a whale shark, after they retrieved pieces of fish skin, though they can't say for sure it was the same one seen by the rig.

But social media users reacted furiously, calling for the culprit to be held accountable. Catching endangered whale sharks is illegal in China.

'Old friend'

The whale shark was first spotted and blogged by workers on board the oil rig on 5 May.

The microblog post called the fish an "old friend", though misidentified it as a sand tiger shark. A later post said the same species would swim near the oil rig in May each year.

"That's adorable! I must get to the island tomorrow," says Weibo user "Katherine", who lives in Chengdu, some 1,200km (734 miles) away.

But some others came up with a stalk warning: "Run now dear! I don't want to see you at the Beihai fish market tomorrow," wrote one user, with a crying face emoticon attached.

Image copyright Sina Weibo / Beihai Municipal Givernment Image caption Pictures of the dead shark shocked many people, and this post by the municipal government appeals for information on this case

On 7 May, new pictures were published by a few others, showing a huge dead shark hanging from a crane on the dockside.

Comments exploded online, with many shouting "call the police" and assuming it was the same shark. One user wrote: "It's too cruel! Enough is enough!"

A crying Feifei Li wrote: "It just felt curious and came by to take a look. Why does it deserve that?"

"No wonder these fishes are not coming anymore. You come again, you got killed again. What for?" said a user named Xiao Jun.

'Already dead'

A Beihai police officer said on Tuesday that the two detained suspects - named as Mr Liao and Mr Huang - had told them the shark already dead and decomposing when they caught it, according to the semi-official China News Service (CNS) agency.

They are now detained on suspicion of "illegal acquisition of rare or endangered animal", said the police, and could face imprisonment of 10 years or more if convicted.

The investigation is still ongoing, CNS reported.

A Beihai police official told the BBC they had nothing to add to the report.

Whale sharks are the largest fish in the world, and can grow to a length of more than 13m (40ft).

They are on the Red List of Threatened Species maintained by the International Union for Conservation of Nature and Natural Resources (IUCN). China also lists the species under Category Two of its national list of protected wild animals, making it illegal to hunt and trade.

The Beihai municipal committee of the Communist Party also announced on Tuesday it was investigating the city's fishery chief Chen Quanbiao for "serious violation of discipline", a synonym for corruption in China.

It was not possible to tell whether Mr Chen's removal had any connection to the shark incident, but local state media reported he had been asked to comment on the incident just a day before he was put under investigation.