A Red Shirt rally in Bangkok has a carnival-like atmosphere, 18 Mar 2010

In Thailand thousands of anti-government protesters plan to step up their campaign to pressure the government to resign. Protesters have gathered for a week in Bangkok.

The weeklong anti-government rallies face a test of support this weekend as leaders try to counter a decline in numbers. Organizers say they plan to use a convoy of trucks to block traffic around Bangkok.

Bangkok's summer heat has taken a toll with fewer than 15,000 at the rally site Friday, after more than 100,000 people gathered last Sunday.

The protesters, known as red shirts for the color they wear, support former Prime Minister Thaksin Shinawatra, who was ousted in a coup in 2006. They say the current government is illegitimate since it was put in place after courts removed two pro-Thaksin governments. They demand that Prime Minister Abhisit Vejjajiva call new elections.

Kudeb Saikrajang, a member of the pro-Thaksin Puea Thai Party, says organizers plan to prolong the protests.

"They have to continue the rally as long as possible until the prime minister [Abhisit] has to declare that he will do something about the house dissolution," said Kudeb Saikrajang. "So that strategy is to prolong the rally. The government side seem to think that the people will disperse after sometime and the leaders here try to prove that they government is wrong."

The protests are the largest since April last when red shirt protests turned violent in Bangkok.

So far the latest protests have been largely peaceful with both sides saying they hope to avoid violence.

Buranaj Samatharak, a spokesman for the ruling Democrat Party, says the rallies can continue as long as they are peaceful.

"If they decide to resort to riots, that will need to be addressed," said Buranaj Samatharak. "It's important to maintain peace, law and order and make sure the rule of law exists on our part. But what course they choose to take is up to them."

There are fears that if the rallies drag out much longer, there is a risk of violence. Several grenades were launched into an army base earlier in the week injuring at least one soldier.

Democrat Party sources say there are also concerns over the safety of the prime minister, who has been at a military base in suburban Bangkok where the government is running its command center.