New York - Usher said on Friday he's "sincerely troubled" to learn he appeared at a concert in St Bart's linked to Libyan leader Muammar Gaddafi's family and plans to donate his concert fee to human rights organisations.

Earlier this week, Mariah Carey, Beyonce and Nelly Furtado all renounced their performances at private concerts later revealed to be linked to the family of Gadhafi, whose country is openly revolting against him and who faces an investigation for possible war crimes.

All the singers have promised to give their fees to charity or said they have already done so.

Usher did not perform but was paid to appear at the private concert featuring Beyonce in 2009.

"I am sincerely troubled to learn about the circumstances surrounding the Nikki Beach St Bart's event that took place on New Year's Eve 2009, " he said in a statement released to The Associated Press.

"I will be donating all of my personal proceeds from that event to various human rights organisations."

The statement said Usher made a contribution on Friday to Amnesty International, which the organization confirmed. The group said Usher requested the donation amount be private.

"Amnesty International activists are working globally to press the international community to support Middle East activists. ... Usher's donation will support this urgent work to counter the brutal conditions like those imposed by Gadhafi and other leaders across the Middle East," a statement from the organisation said.

Since the uprising in Libya, attention has focused on entertainers paid by the Gaddafi family for private concerts. Furtado acknowledged getting $1m, which she promised to give to charity.

Beyonce said she donated her fees for to Haiti earthquake relief once she discovered the Gaddafi link.

Carey said she was unaware of whom she was performing for and "embarrassed." She announced she will donate royalties for the song "Save the Day," which she has written for her upcoming album, to charities that create awareness for human-rights issues.