BANGKOK (AFP) - Thousands of supporters of ousted premier Thaksin Shinawatra rallied outside Thailand's main government offices in Bangkok Saturday, vowing to fight on until the new administration left office within 15 days. The protesters spent nearly two hours marching towards Government House, arriving just before midnight (0500GMT) after making their way past four steel barricades across their route, manned by unarmed riot police. "We have arrived at Government House... We are not going to go inside," said rally leader Nattawut Saikuar. Rally leaders earlier said they would remain outside Government House, where they would read a list of demands that include the dissolution of government, before dispersing. Around 30,000 protesters gathered in the evening at Sanam Luang park in Bangkok to hear protesters' speeches before the crowd set off, led by more than 100 motorbikes and 10 trucks carrying rally leaders. Police deployed 5,250 officers in response to the rally, Lt-Gen Suchart Mueankaoe, commander of Bangkok Metropolitan police, told AFP, with many more on standby along with the army. Many officers lined the 4km route to Government House, fearing a repeat of a three-month siege by rival protesters that began last August. Saturday's protesters - known as the "Red Shirts" because their crimson clothes show they oppose the yellow-clad, anti-Thaksin People's Alliance for Democracy (PAD) - gave the government 15 days to leave before staging a permanent protest. "The government has 15 days (to leave). From then, no matter how long we have to protest we will do it," rally leader Jatuporn Prompan told the cheering crowd. "If the government uses force... this government will not last until tomorrow," he added. The crowd was in good spirits during its march, waving Thai flags and foot-shaped clappers as they walked past police, encountering delays only at the fourth barricade that was heavily fortified with chains and barbed wire. The Red Shirts are calling for those involved in a siege of Bangkok's airports last year to be fired from government jobs and then prosecuted, and for parliament to be dissolved. Organiser Jakrapob Penkair said the government was illegitimate and accused the army of staging a silent coup to bring it to power. "We have experienced several fights, several coups, but there is no fight as important as this one because we have to fight to bring back our nation," said Jakrapob. "How can the party that lost in elections three times become the government? The army denies being involved in setting up this government but no one believes them anymore," he added. Speaking earlier on the sidelines of the World Economic Forum at Davos in Switzerland, Prime Minister Abhisit Vejjajiva said he was not worried by the rally. "I think the mood of the people now is that they very much want to move forward, they want to get over the current divisions, they want to see a government that works hard, that deals with people's concerns and has the honesty and integrity that has been missing for so long," Abhisit said. "If we can keep on working in the way we have for the last month then I'm not worried about it," he said, adding that deputy prime minister Suthep Thaugsuban would ensure there was no repeat of last year's siege.