Tens of thousands of demonstrators rallied in Bangkok on Sunday, demanding the Thai government dissolve parliament and call new elections.

A supporter of ousted prime minister Thaksin Shinawatra holds a poster during Sunday's protest. (Sakchai Lalit/Associated Press)

Supporters of ousted prime minister Thaksin Shinawatra marched through the streets and gathered at one central location, then threatened to spread out across the city with the intent of paralyzing the capital if the government doesn't call elections by noon Monday.

Demonstrators donned red shirts and got into trucks, buses and cars, most of them travelling from rural areas, to take part in the rally.

They're protesting against political developments since 2006, when Thaksin was ousted by the military in a bloodless coup for alleged corruption and abuse of power.

A party formed from the ashes of Thaksin's Thai Rak Thai Party was elected to form the government in 2007, but that government was ordered disbanded by the courts for electoral fraud. The opposing party, made up of mainly of Thailand's Bangkok-based elite, was once again restored to power.

The protesters, formally known as the United Front for Democracy and Against Dictatorship and popularly known as the Red Shirts, staged a similar demonstration in Bangkok last April.

Army called in

The event deteriorated into rioting that left two people dead, more than 120 people injured and buses burned on major thoroughfares. The army was called in to quash the unrest.

This time, the demonstrators stress they will use only peaceful means.

However, the government has been bracing for unrest. It has invoked special emergency laws and has put about 50,000 soldiers and police on the streets.

In his weekly radio address Sunday morning, Prime Minister Abhisit Vejjajiva indicated he had no plans to dissolve the legislature.

"Dissolution and calls for resignations are normal in a democratic system. But we have to make sure the dissolution of parliament will solve the problem and won't make the next election troublesome," Abhisit said.

With files from The Associated Press