Species of shark that killed surfer Serge Bideau off Reunion island in Indian Ocean has yet to be identified Wikimedia Commons

A 22-year-old surfer has been killed by a shark in the Indian Ocean waters off the French outpost of Reunion island, authorities said.

Government spokesman Serge Bideau said the man was in an area popular with surfers when a shark attacked and bit off his right leg.

Witnesses helped the victim, identified as island resident Alexandre Rassica, to shore where rescue workers tried in vain to resuscitate him.

It was not known what type of shark attacked him.

The number of shark attacks has risen in the waters off Reunion over the last two years and the authorities are trying to find out why. There have been seven attacks - not all fatal - since the start of 2011.

The death came less than a week after 24-year-old Benjamin Linden, of Perth, Western Australia, was attacked by a great white shark 600ft (200 metres) off Wedge Island, a popular family holiday spot.

A jet-skier saw blood in the water and rushed to help the victim but he was too late. By the time he got there Linden's body had been bitten in half by the shark.

The attack led to calls by the Western Australia state government for protected status to be lifted from great white sharks.

Similarly, in Reunion there has been anger over the fining of fishermen for hunting sharks that have been blamed for attacking humans.