US singer Erykah Badu has been condemned as a hypocrite for singing "Happy Birthday" to Swaziland's King Mswati III, described by a rights group as a "corrupt tyrant". The hip-hop and soul singer performed for the king at his official 46th birthday celebrations during a visit to the southern African country last Thursday, leaving the US-based Human Rights Foundation (HRF) fuming. "She owes us all an explanation. The king is a kleptocrat who lives in the lap of obscene luxury while most of his countrymen toil in abject poverty for less than $2 a day," HRF's Alex Gladstein said in a statement. American jeweller Jacob Arabo brought the Grammy award-winner to Swaziland as a birthday gift for Mswati, considered Africa's last "absolute monarch", according to state-run Observer newspaper. "This is my second time in Swaziland and the last time I was here there were a lot of women dancing in a forest," the newspaper quoted her as saying before dedicating her first song to "sons of kings". She gave Mswati a $100-bill as a birthday present, as well as "a special stone which she said would uplift His Majesty's spirits when he was feeling down," according to the newspaper. Two years ago, Mswati celebrated his birthday by ordering his subjects to give him cows. Badu's support of the king goes in the face of her self-professed concern for human rights, according to HRF. "She claims to want to improve the lives of the disenfranchised and impoverished, but unapologetically does favours for a corrupt tyrant who jails those who challenge his ill-gotten wealth and power," said Gladstein. Two journalists are on trial in Swaziland for writing articles critical of Mswati's government. Africa's last absolute monarch holds a tight grip on dissent in his tiny mountain kingdom, where criticism of the king is illegal