Seoul - Organisers of next month's world swimming championships in South Korea are facing the prospect of half-filled grandstands, figures showed on Friday, with only around one-third of tickets sold.

A total of 419 000 tickets are available for the FINA World Championships taking place in the southern cities of Gwangju and Yeosu, from July 12-28.

But only about 149 000 have been taken up since they went on sale in January, organisers said on Friday - just over 35 percent.

Around 140 000 of those were block-bought by companies, municipal governments and state-owned firms, meaning that private individuals had bought merely 9 000 or so, about two percent of those available.

"Not many would travel all the way to Gwangju to see watersports in the summer," one of the organisers acknowledged to AFP.

"Especially considering the competition will be broadcast live throughout the event."

South Korea is Asia's fourth biggest economy and a regional sporting power, one of only two Asian countries - alongside Japan - to have hosted both summer and winter Olympics.

But swimming was largely unpopular in the South until quadruple Olympic medallist Park Tae-hwan won gold in the 400-metre freestyle at the 2008 Beijing Games, the country's first victory in the pool.

The star nicknamed "Marine Boy" has struggled since, and was stripped of his medals from the 2014 Asian Games in Incheon after testing positive in out-of-competition controls and banned for 18 months.

Ticket prices for the biennial world championships range from 10 000 won to 150 000 won ($125), with the Seoul Metropolitan Government among the biggest purchasers after taking 1 billion won-worth - $850 000.