Rapper Nelly insists he is "completely innocent" of sexual assault allegations following his arrest for rape in Washington state.

The Hot in Herre hitmaker was taken into custody and booked on charges of second degree rape in the early hours of Saturday (07Oct17) morning and the 42-year-old has hit out against accusations he molested an unnamed women on his tour bus.

"Let me say that I am beyond shocked that I have been targeted with this false allegation," he wrote on his Twitter account. "I am completely innocent. I am confident that once the facts are looked at , it will be very clear that I am the victim of a false allegation."

Nelly moved on to share his regrets over how the situation has impacted his family and friends.

"I do want to apologize to my loved ones for the embarrassment and for putting myself in a situation where I could be victimized by this false and defaming allegation," he tweeted. "I also want to thank my fans for their unwavering support. They know me. I assure you I will be vindicated. And I assure you, I will pursue every legal option to address this defaming claim."

"In other words y'all know damm well I ain't do no dumm S^*t like this..!! Love ..!!!!," he wrote, before clarifying he has not been formally indicted on rape charges: "To be absolutely clear. I have not been charged with a crime therefore no bail was required. I was released (from custody), pending further investigation."

His lawyer Scott Rosenblum is also convinced his client will be fully vindicated after police officers complete their investigation.

"Nelly is the victim of a completely fabricated allegation," the attorney wrote in a statement to Variety. "Our initial investigation clearly establishes this allegation is devoid of credibility and is motivated by greed and vindictiveness.

"I am confident, once this scurrilous accusation is thoroughly investigated, there will be no charges. Nelly is prepared to address and pursue all legal avenues to redress any damage caused by this clearly false allegation."

Nelly, real name Cornell Iral Haynes Jr., was scheduled to perform in Ridgefield, Washington on Saturday night as part of his ongoing tour with country duo Florida Georgia Line before he was apprehended by police.

This isn't the first time he has gotten in trouble for alleged crimes on his tour bus. The star was arrested in 2015 for felony drug possession after state troopers discovered narcotics paraphernalia on his personal tour vehicle.