Tens of thousands of protesters riding motorcycles and crammed into trucks and cars have rolled through the streets of the Thai capital to rally residents to their "class war" against the government.

The Red Shirt protesters plan to follow up the march with a giant painting made from their own blood, the latest shock tactic in their week-long campaign to oust the government of Prime Minister Abhisit Vejjajiva.

The mass protest stretched at least six miles along Bangkok's streets, and Metropolitan Police commander Vichai Sangparpai estimated the number of participants at 100,000.

Large crowds cheered the procession from the pavements as it passed with red flags and ribbons fluttering and car horns honking. Some motorcyclists plastered their licence plates with stickers reading "The Red Shirts love Bangkok people".

"Please come out into the streets to change Thailand. Time waits for no one. No matter what colour of shirt you wear - it doesn't have to be red - you can join our cause if you love equality and democracy," a protest leader, Natthawut Saikua, said as onlookers showered him with red roses.

The procession included rural pick-up trucks, taxis, minibuses, luxury sedans and Bangkok's iconic three-wheeled "tuk-tuks".

The protesters want Mr Abhisit, whom they accuse of taking power through illegitimate means, to dissolve parliament and call new elections - a demand he has repeatedly rejected. Mr Abhisit has been sleeping and working at an army base for the past week to avoid the demonstrators.

The protesters planned a 40-mile loop through Bangkok, setting off from their encampment in the historic centre of the city and driving through the central business district, Chinatown and outlying residential areas.

Protest leaders have increasingly portrayed the week-long demonstrations as a struggle between Thailand's impoverished, mainly rural masses and a Bangkok-based elite impervious to their plight.

The group largely consists of supporters of former prime minister Thaksin Shinawatra, who was ousted by a 2006 military coup for alleged corruption, and pro-democracy activists who opposed the army takeover. Mr Thaksin is popular among the rural poor for his populist policies. They believe Mr Abhisit came to power illegitimately with the connivance of the military and other parts of the traditional ruling class and that only new elections can restore integrity to Thai democracy.