SANTIAGO (Reuters) –- Mention extreme sports and mountaineering, bungee jumping or white-water rafting come to mind. But in Chile it is kite flying that causes accidents, claims lives and generates a big official headache.

In September and October when strong winds blow during the southern hemisphere's spring, children and adults crowd the parks and streets of this South American nation, flying simple rectangular kites made from tissue paper.

In the capital's working-class playground, the enormous O'Higgins Park, colored squares fill the sky and litter the trees. Dozens of kite clubs set up booths hawking specialized string, enormous wooden spools and other paraphernalia.

Packs of boys carrying 12-foot-long (four-meter-long) poles run around the parks jostling each other to fish kites out of the sky after they have been cut down by rival kite fliers using razor-sharp string. On Chile's national independence day on September 18, an estimated four million people, or a quarter of the country's population ventures out with kites -- which come as cheap as 27 U.S, cents each -- designed as the Chilean flag or the insignia of favorite soccer teams.

But as this long, thin country between the Pacific and the Andes gains prominence in competitive international sport kite-flying, hundreds of children are injured every year in the dangerous seasonal ritual.

Kite-flying is not just a family day out but a competitive game in which participants try to cut down other kites using a string cured with glue and pulverized glass, giving it a knife-like edge.

In Chile there is an average of one kite-related death per year and hundreds of injuries, according to Mario Reyes of Chile's Safety Association.

Children get electrocuted as their kites become tangled in overhead cables and the string conducts electricity.

Others are injured climbing onto roofs, shinning up electricity poles, falling into holes and darting in front of traffic to retrieve their kites. "Kites produce a sort of psychosis in children. When a kite is cut, there is not one but dozens of children running after it," says Reyes.

Kites have even killed innocent bystanders. In September a 19-year-old university student was decapitated as he became entangled in a kite string that crossed the road where he was riding his motorcycle. --------Power Outages-----

Kites are also responsible for 200 power cuts per year which happen when it rains on a overhead cable damaged by a kite, according to Chilectra, an electricity distributor that serves Santiago.

"A typical kite-related power cut can leave 15,000 people without electricity for a night," said Marcelo Castillo, head of communications at Chilectra.

Authorities took steps this year to contain the problem, distributing safety information to 11,000 schools.

This year cities designated "safe" areas for kite lovers. The safety association is campaigning to ban cured string and has held public burnings of heaps of the dangerous kite string. Competitors in professional contests now have to use lightweight cotton string that breaks easily and is cured with ground quartz, which is allegedly safer than glass.

"The quartz is so fine you could eat it and it wouldn't do you any harm," said Cristian Fernandez, head of Chile's Kite Club Association.

But some people accept the danger is part of the fun.

"The danger doesn't worry me. We're used to it, we know what we're doing," said Fabian, a 25-year-old who has been flying kites since he was a toddler.

While Asian countries such as China, Indonesia, Malaysia and Japan have been flying kites for centuries, relative newcomer Chile -- where kite-flying caught on in the mid-1800s -- is catching up with Asia in international competitions. Last year Cesar Gutierrez came second in the world championships in France.

While elsewhere in Latin America in Brazil and Colombia kite flying is popular, it does not reach the fanaticism of Chile, says Fernandez.

According to Gutierrez other countries do not have the same accident rate as Chile because with years of experience they have enforced strict regulations.

"Kite-flying regulations in Chile are a mess because the activity has only recently passed from being a pastime to a professional sport," said Gutierrez.

Most accidents happen due to ignorance, he said, noting that some people have used copper wire to fly kites dangerously close to power lines. "I think that if people are educated, any activity is going to be safer," he said.