Around 150 nude cyclists have participated in the annual bike ride bringing shock to onlookers and residents as they swept inner-city Melbourne in promoting bike activism.

According to the Australian Associated Press, this year is Melbourne’s fourth annual “Naked Bike Ride” with creative slogans and relevant issues being supported and helped promote awareness of.

Some of these issues raised by participants include the situation in Libya, scandals and issues hounding prominent political leaders; bike activism and call for freedom. And these issues were painted very creatively and strategically in the bikers’ naked bodies.

"Slogans are fantastic this year. They're quite political," the event’s organizer, Heidi Hill told AAP. "There's some to do with the Libyan situation. There is Berlusconi this year. Mostly it's about freedom and about bike activism, like 'please cycle safely', and 'bike love'."

But AAP noted that this form of bike activism have stunned onlookers and Melbourne residents as the ride kicked off at the Edinburgh Gardens in North Fitzroy. The event had taken the naked riders on a 10-kilometre trip through the city’s streets.

Hill underscored that bare biking is one best way to get the attention of the public as well as the government officials and help them understand various issues such as naturism, environmentalism and pacifism.

And the naked bikers are doing this while having fun at the same time and bringing big smiles to those watching on the streets.

"Going past Lygon Street and all the restaurants, people come running out and they're quite shocked and then they start laughing and screaming," Heidi was quoted as saying by the AAP.

Hill suspects only reason why Sunday’s naked bike ride was a success.

She said, "I think people are titillated and excited to see people having so much fun."