South Africa Women's Institute of Migration Affairs (SAWIMA), which liaises with the government's Lindela Repatriation Centre, outside Johannesburg, where undocumented and illegal foreigners are held before being repatriated, said it picked up at least five unaccompanied minors from the centre every week.

"What is of grave concern is that the children are getting younger - they are aged between 10 to 14 years now," said Joyce Dube, a member of SAWIMA. "This week we picked up a four-year-old from the centre, who we managed to reunite with relatives."

Some of the unaccompanied minors have been sent for by their parents, who have settled in South Africa, but Dube said most others had been driven across the border by hunger. "Many children cannot afford to go to school any more - they just hang around doing nothing, and have no means to earn money, to eat - so they cross the border illegally to find work."

Unable to raise funds for a passport or visa, they often trade sex with truck drivers or taxi drivers for smuggling them across the border. "They end up as child labour, working for small wages or, at times, for nothing at all," said Dube.

Taxi operators plying across the border charged about US$200 per head, paid by Zimbabwean parents to have their children brought to South Africa. "If they [children] are apprehended, we help to reunite them with their families here," Dube explained.

Figures released by humanitarian agencies showed that more than 2,100 children - a daily average of 14 - without birth certificates or any other form of identification were deported from South Africa to the border town of Beitbridge in southern Zimbabwe in the first five months of 2006.

According to the International Organisation for Migration (IOM), in the last six months of 2006 almost 950 unaccompanied children passed through a reception and support centre in Beitbridge, which has a child centre to accommodate deported children pending family reunification. The centre is jointly run by the IOM, Save the Children (Norway), United Nations Children's Fund (UNICEF) and Zimbabwe's Ministry of Public Service, Labour and Social Welfare.

"These young people are doing it [crossing the border illegally], perhaps because they feel there is a lack of opportunities at home. Some of the 15-to-16-year-olds will be looking for financial opportunities to look after their siblings back home," said James Elder, the UNICEF spokesman in Zimbabwe.

Child trafficking and illegal migration needed a more holistic approach, said Elder. "It is obvious these children can't find employment, and risk being exploited in the most grotesque manner. They have no skills, and have to compete with adults for job opportunities across the border."

The European Commission's Head of Delegation to Zimbabwe, Ambassador Xavier Marchal, said the EU considered the promotion of child rights a priority and has provided $1 million to help children access legal documents and create awareness about illegal migration. "Tackling child trafficking and illegal cross-border migration would help to address commercial sex work involving girls living on the streets in major towns and cities," he said.

Since July 2006 the EU has bolstered support for the child centre in Beitbridge, which has provided food, clothing, blankets and psychosocial support services to 1,000 children.

Part of the EU donation will also be used to train traditional leaders, guardians and community members about the risks of crossing borders without documentation, and a second child reception centre at Plumtree, on the Botswana border in southwestern Zimbabwe, is planned.

Funds will also go towards increasing the number of children with birth certificates by 25 percent in Zimbabwe's 10 districts over a period of two years, to meet a major objective of the National Plan for Orphans and Vulnerable Children. Besides providing migrating children with legal status, the birth certificate programme will help other vulnerable children in Zimbabwe.

"Without a birth certificate, children are often denied their rights and cannot enroll in school or gain access to basic health services. The problems is exacerbated for orphans, for they risk [losing] all inheritance from their deceased parents when there is no proof of lineage," said Marchal.

UNICEF's representative in Zimbabwe, Dr Festo Kavishe, said children without birth certificates were invisible to society. "Such children lack the basic protection against abuse and exploitation: they are highly vulnerable to unscrupulous child traffickers, abusive employers or illegal deportation agents."