Embattled rapper Rick Ross has issued an apology to fans and business partners after coming under attack for appearing to condone rape in the controversial lyrics for new song U.O.E.N.O. (You Ain't Even Know It).

The heavyweight hip-hop star sparked furore in his verse on rapper Rocko's single, in which he spits, "Put molly all in her champagne/ She ain't even know it/ I took her home and I enjoyed that/ She ain't even know it."

The reference to "molly", slang for pure ecstasy, enraged women's rights activists who accused Ross of condoning date rape with his lyrics, and an online petition was launched by UltraViolet anti-sexism campaigners calling on bosses at sports giant Reebok to drop the rapper from his sponsorship deal.

Reebok executives declined to comment or take action over the controversy, prompting demonstrators to stage a protest outside their New York headquarters on Thursday (04Apr13).

As the activists gathered to deliver the petition signed by 72,000 supporters and called for Ross to be axed as a celebrity spokesman, the rapper took to his Twitter.com page to try to make amends for his lyrics, writing, "I dont condone rape. Apologies for the lyric interpreted as rape..."

He also reached out to Reebok, adding, "Apologies to my many business partners, who would never promote violence against women."

However, his lacklustre apology did little to quell UltraViolet members' anger.

In response to his Twitter apology, a representative replied, "We appreciate that you don't condone rape but what's upsetting is that you're rapping about it & don't know it... slipping a woman a drug and 'enjoying' her is rape."