A shy smile creeps across the hardened face of 17-year-old street kid Siyabonga Mkhize as he proclaims proudly: "I am playing soccer for South Africa!"

He is one of about 500 people from nearly 50 countries taking part in the fourth Homeless World Cup that started in Cape Town on Sunday in an attempt to transform their lives.

Mkhize, a goalkeeper for the South African squad, said he was kicked out by his parents over his drug habit a few months ago. He sleeps under cardboard boxes on the street and works as a car guard to get money for food.

"I want to change my life," he said at a practice session last week. "I stopped taking drugs two weeks ago. I want to go back to school and study to become a social worker."

Playing soccer, a passion, appears to have given him new hope.

"I am feeling good, because I am playing for my country," he said. "I like the Kaizer Chiefs [a local South African team]. Maybe one day I'll play for them."

James Steenberg, 18, has lived in a homeless shelter in Cape Town for the past 11 years after being abandoned by his parents. He plays right wing and defence for the South Africans, and hopes to be spotted by talent seekers.

"I believe this World Cup will give me exposure. I want to play one day for a team like Manchester United or Chelsea," he said, adding that he was "not half bad".

Event organiser Mel Young said nearly 80 per cent of players competing in past tournaments had got a new lease on life by finding a job or a home, registering for occupational training or weaning themselves off drugs.

"You can coach homelessness out of these players," he said ahead of the week-long event.

"Getting involved in sports changes their mindset and gives them self-esteem. Sport can be used as a method of changing people's lives."

Young is president and co-founder of the Homeless World Cup, a non-profit social enterprise registered in Britain.

The annual event is sponsored by businesses, governments and voluntary organisations which provide the players' kits, accommodation and travel costs.

The tournament comes four years before South Africa hosts the "real" World Cup, the first time the event has been staged on the continent.

Young said some participants in the past three tournaments had since taken control of their lives and become sports coaches, salesmen or teachers. One was training to become a motor mechanic.

"The confidence he gained from playing football convinced him he was able to do this job," he said.

The participants became homeless for reasons ranging from abject poverty to psychiatric problems or abandonment, Young said. Many became alcohol or drug addicts.

Players are required to be drug-free and sober for three months prior to the tournament.

Some were bad soccer players, Young said with a laugh. "In fact, some are terrible. That is why we have different levels of competition in the tournament."

Countries from all continents are participating in the event, including Chile, Russia, Kazakhstan, the United States, Australia, Rwanda and Liberia. Some, like Britain, are coached by professionals.

Italy have won the cup for the past two years.

Players are identified by volunteers holding training sessions at homeless shelters around the world.

The tournament will be played out in four-a-side matches on the streets around Cape Town's Grand Parade, rather than in stadiums. "It seems appropriate since the players are from the streets," said Young.

Errol de Villiers, a 23-year-old former street kid from Cape Town who has abandoned crime and drugs, now has new dreams.

"I want to go and play overseas," he said. "I hope somebody will give me a chance."