Jennifer Lopez apologized on Monday after singing on the weekend for the president of petroleum-rich Turkmenistan, considered to be one of the world's most oppressive regimes.

The artist attempted to clarify what had occurred after being criticized by the Human Rights Foundation for her performance on Saturday.

Lopez sang at a non-political event sponsored by the China National Petroleum Corporation, her publicist said Sunday.

"Had there been knowledge of human rights issues any kind, Jennifer would not have attended," the publicist said in a statement.

Lopez sang "Happy Birthday" to Turkmenistan's president, Gurbanguly Berdimuhamedow, after CNPC asked her to do so at the last minute before she was due to take the stage.

The artist's manager, Benny Medina, told the TMZ Web site that the singer's team did not know that the president was present at the event until a few moments before Lopez began to sing.

The engagement in Turkmenistan came just a few weeks after J.Lo appeared with Beyonce at a concert in London to benefit Chime for Change, an organization seeking to promote the development of disadvantaged girls and women worldwide.

In March 2011, Lopez rejected an offer of up to $2 million to perform at a private concert for Libyan leader Moammar Gadhafi and his family.

Other stars, including Beyonce, Mariah Carey, Nelly Furtado, Usher and 50 Cent, did perform for the Gadhafi clan, though several of them later donated their fees to charity.

Turkmenistan, according to Human Rights Watch, is one of the "most repressive" countries in the world. EFE