They plan to follow up the march with a "blood painting" on Sunday, the latest shock tactic by the so-called "Red Shirts" in their peaceful, weeklong campaign to oust the government of Prime Minister Abhisit Vejjajiva.

City and police officials, fearing massive traffic jams, urged residents to use public transport and either stay at home or at their workplaces until the demonstration ends.

The procession was cheered from the sidewalks by large crowds as it passed with red flags and ribbons fluttering and car horns honking. Some motorcyclists plastered their license 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 color 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 caravan included rural pick-up trucks, taxis, mini-buses, luxury sedans and Bangkok's iconic, three-wheeled "tuk-tuks." The protesters want Abhisit, who they accuse of taking power through illegitimate means, to dissolve Parliament and call fresh elections - a demand he has repeatedly rejected. Abhisit has been sleeping and working from an army base for the past week to avoid demonstrators.

"The prime minister we have is bad. We want to take him down. The economy is not good. I don't have a problem with the demonstration. I've lived in Bangkok a long time. I can handle any kind of situation," said Sudarat Pumprparn, a 47-year-old maid as many around her shouted "Get out (Abhisit)." The protesters plan to loop their way for some 40 miles (70 kilometers) through Bangkok, setting off from their encampment in the historic center of the city and driving through the central business district, Chinatown and outlying residential areas.

The size of the protest peaked Sunday at some 100,000 demonstrators, but has decreased by about half since then.

In an attempt to dramatize their demands, thousands of Red Shirts lined up Tuesday to donate blood to their cause.

Leaders claimed they collected 80 gallons (300,000 cubic centimeters) of blood that were transferred into dozens of large plastic jugs.

Most of the blood was splattered at Abhisit's office, at the headquarters of his ruling party and at his private residence.

Protest leaders say they have 15 jugs of blood left and plan to use it to create a massive work of art.

"Artists and Red Shirts will be invited to partake in a blood painting," Jatuporn said. They plan to unfurl a giant white cloth on which supporters will be invited to paint pictures, scrawl poems and express political statements.