Stockholm - Former South African president Nelson Mandela and his wife Graca Machel were Friday named winners of a children's rights prize in a vote involving over 7 million children worldwide.

"We are extremely honoured to have been voted as the Decade Child Rights Heroes," Mandela and Machel said in a statement issued by organizers.

"For both of us this award is very, very special given the place children occupy in our hearts and lives," they added.

Mandela and Machel were selected among 13 former winners of the World's Children's Prize, organizers said.

The prize was worth a total of 1.1 million kronor (160,000 dollars) of which Mandela and Machel were to receive 500,000 kronor. The other 12 nominees were to share the rest of the prize sum.

The award ceremony was set for April 26 in Stockholm, spokesperson Andreas Lonn said.

The tally of the vote was not disclosed since "all the nominees were winners," Lonn explained.

The announcement was made in conjunction with the 20th anniversary of the United Nations Convention on the Rights of the Child.

Mandela was cited for his "lifelong struggle to free the children of South Africa from apartheid, and for his unwavering support for their rights."

Machel was lauded for her work for vulnerable children, not least in her native Mozambique and has championed the right for girls to go to school.

Patrons of the World's Children's Prize include Queen Silvia of Sweden, Mandela, East Timor President Xanana Gusmao, Carol Bellamy the former head of UNICEF, and Nobel economics prize laureate Joseph Stiglitz.

The award was established in 2000 by the Swedish non-governmental organization, Children's World.

Former winners include Betty Makoni of Zimbabwe who has sought to empower girls in the southern African nation, and Somaly Mam of Cambodia who has campaigned against trafficking and child prostitution. (dpa)