Britain's Prince Harry has been spotted partying alongside a mystery blonde in Las Vegas.

The 27 year-old royal - who is currently based in the US to complete his Royal Air Force training - rode into Sin City on Friday night on a $17 000 Harley Davidson motorbike as he prepared for a weekend-long break from his military commitments.

An onlooker told the Mail On Sunday newspaper: "Harry was grinning from ear to ear and he jumped on the bike like a natural. He didn't look the least bit nervous when he roared off, but he had quite an entourage with him.

"They kept their distance as it was clear he was just enjoying the freedom of being on the open road."

Checking into the city's exclusive Wynn Hotel, the party-loving prince was seen boogying into the early hours of Saturday morning at the hotel's Tryst Nightclub where he seemed particularly taken with the blonde, who he sat on a sofa chatting to and later enjoyed a "seductive" dance with.

Continuing his weekend in style, on Saturday night Harry was spotted in the front row of Cirque Du Soleil's 'O' at the Bellagio hotel, where he gave the performers a standing ovation before being whisked away by security before the house lights were turned on.

The prince then moved on to a spot of gambling and despite he and eight friends losing $500 in total, Harry "couldn't believe" the number of free drinks he was given.

A source told People magazine: "He lost $300 gambling and his friends lost $200. He couldn't believe you got free drinks from gambling at the blackjack tables."

The royal then moved on to XS nightclub for a more "low-key" session than the previous evening, where he was said to have kept a low-profile and sat at the owner's table all night.