U.S. pop singer Madonna appeared in a Malawi court today seeking to adopt a second child, a girl called Mercy James, from the southern African country.

Critics had accused authorities of giving the singer special treatment when she adopted her Malawian son David Banda from an orphanage in 2006. Malawi civil society groups say they plan to oppose Mercy's adoption.

Madonna appeared at the court in a black dress and sunglasses, said a Reuters witness.

One of Madonna's lawyers told reporters outside the court that she was asking the court to grant her an interim adoption of about 18 months of Mercy, who is four years old.

The local Nation newspaper has quoted Madonna, 50, as saying Malawian friends had told her David needed a brother or sister.

Madonna took David when he was 13-months-old after his father placed him in an orphanage following the death of his wife.

The singer has said despite the controversy around David's adoption, she was happy to be involved in a case that might pave the way for more adoptions in Malawi, where an estimated one million children have been orphaned by AIDS.