Grieving fans mourned the death of pop star George Michael as British charities praised his behind-the-scenes generosity on behalf of numerous causes.

The singer's death was announced late Sunday. Many paid tribute on Facebook and Twitter and others cited years of good works that received little publicity.

Fans placed flowers and other tributes at his homes in north London and in Goring, England, where he died of apparent heart failure.

Michael's later years were marked by occasional brushes with the law and a series of driving incidents related to substance abuse, but another side emerged Monday as top charity figures stepped forward to thank Michael for years of donations and good works.

Among the groups he supported were the Terrence Higgins Trust, which helps people with AIDS, Macmillan Cancer Support, and Childline, which offers confidential phone counseling for young people.

Childline founder Esther Rantzen said Michael gave royalties from his 1996 hit "Jesus To A Child" to the charity along with many other donations.

"Over the years he gave us millions and we were planning next year, as part of our 30th anniversary celebrations to create, we hoped, a big concert in tribute to him -- to his artistry, to his wonderful musicality but also to thank him for the hundreds of thousands of children he helped," she said.

She said Michael was determined that no one outside the charity should know "how much he gave to the nation's most vulnerable children."

Jane Barron from the Terrence Higgins Trust said Michael made many donations and gifts, including the royalties of his "Don't Let the Sun Go Down on Me" duet with Elton John in 1991.

Michael had spoken publicly about the pain of losing a partner to AIDS early in the epidemic, but he kept his long history of donations to the Trust private.