JOHANNESBURG (AFP) - South African thieves are invading ostrich farms and poaching feathers from the giant birds, in a crime that has baffled local farmers, an industry chief said on Tuesday.

"This started during the last six weeks," said Mr Piet Kleyn, the chief of the South African Ostrich Business Chamber.

He said thieves sneaked up on the birds at night and plucked their feathers without using proper tools.

"The frightened birds are badly treated and some die because of the terrible injuries," Mr Kleyn told AFP.

At least 50 birds in the ostrich-rearing region of Oudtshoorn, in the Western Cape, have been attacked in recent months.

According to Mr Kleyn, even birds with feathers that had not yet fully grown were targeted.

The cause is not known, but it is believed that the trend is driven by good market prices for ostrich feathers.

The feathers are much sought after in the fashion industry. They are also used to accessorise carnival costumes and make feather dusters.

The South African ostrich industry is often hampered by a ban on meat export, due to avian influenza outbreaks.

South Africa is the leader in ostrich production with 75 per cent of the global market share.