A famed dusky shark in South Korea has returned to the canal where she had been stuck for a month, just one day after authorities said they had successfully guided her out, local media report.

The shark, nicknamed Bukangi, became an unlikely sensation after she was spotted lingering in a canal in the south-eastern port city of Busan last month.

South Korea's oceans ministry said on Wednesday evening they had led Bukangi out of the canal into an open harbour - but reports later said the shark had swum back to the mouth of the canal, having apparently broken through a barrier installed by authorities.

Another operation to relocate Bukangi has been scheduled for Thursday.

It is thought that Bukangi might have been drawn to the canal by unusually warm waters and plenty of fish. With the sea getting warmer each year, experts say Busan may play host to more sharks in the future.

In the month that she has been in the canal, Bukangi has already attracted more than 1.6 million visitors.

Her popularity gave a welcome boost to Busan's tourism, and the city has embraced her as an unofficial mascot.

But authorities were also concerned about Bukangi's well-being as she appeared to be injured and was not eating. Social media users have been circulating videos of Bukangi swimming in the canal with what appears to be a bloodied snout.

There were concerns that she would be further weakened by falling water temperatures.

In a livestreamed operation on Wednesday, rescue workers took more than eight hours to delicately guide the three-metre-long (10ft) shark with a net towards open water in a harbour.

Hundreds of adoring fans cheered and waved goodbye to their shark, unaware that she would still be lingering in the canal by the next day.

Before Wednesday's operation, there had been two earlier failed attempts to guide Bukangi out of the canal with nets. (BBC)