BANGKOK: Thousands of Thai demonstrators marched on Wednesday towards a government office complex they planned to shut down as part of efforts to cripple the government and oust Prime Minister Yingluck Shinawatra.

Having forced the closure of five ministries in the past two days, about 4,000 protesters rallying against Yingluck and her influential brother, former premier Thaksin Shinawatra, aimed to surround the complex in northern Bangkok while smaller groups readied to target six other ministries.

The demonstrations are familiar in Thailand, which has seen eight years of on-off turmoil, from crippling street protests to controversial judicial rulings and military intervention,each time with Thaksin at the centre of the disputes.

The demonstrations have been going on for weeks but are gaining momentum. In response to a rousing speech by protest leader Suthep Thaugsuban screened on cable television late on Tuesday, demonstrators in 10 southern provinces massed in front of government offices, according to police.

Despite fleeing into exile to dodge a jail sentence for abuse of power in 2008, billionaire former telecommunications mogul Thaksin has loomed large over Thai politics.

He won the support of the rural poor who voted him twice into office, in 2001 and 2005, before he was ousted in a 2006 military coup. His supporters remain fiercely loyal to him and the parties he backs.

His opponents are fewer in number but hold considerable power and influence, among them wealthy conservatives, top generals, bureaucrats and royalists with sway over the urban middle class.

Many of them see Thaksin as a corrupt, crony capitalist who manipulates the masses with populist handouts and is a threat to the monarchy, which he denies.

“Today we march again. I will lead you myself. Those who are ready, line up,” Suthep, leader of the Civil Movement for Democracy, as the largest protest group is known, told thousands of protesters who had camped overnight at the Finance Ministry in Bangkok.

Suthep led his group towards an office centre containing important government agencies, including tax, revenue, immigration and land departments.

It also houses the Supreme Court and headquarters of Thailand's Department of Special Investigation, its equivalent to the US Federal Bureau of Investigation.

Electoral Mandate

Another group of 1,000 protesters marched to the Labour Ministry and some splintered off towards the Energy Ministry.

Firebrand protest leader Suthep, a deputy Prime Minister in the previous government, told cheering crowds their target was to wipe out the “political machine of Thaksin”.

The protests, though peaceful, have raised fears of a repeat of the sort of violence seen three years ago when more than 90 people were killed in a military crackdown on demonstrations by Thaksin's supporters.

Suthep, then in government, is accused of ordering the crackdown and he was recently indicted for murder.

Anti-government protest leaders, from all sides, have a tradition in Thailand of trying to provoke a violent crack down by the government to rob it of legitimacy.

Fearing clashes could erupt and further weaken her government, Yingluck said police would keep the peace.

“My government will not use force. This is not the 'Thaksin regime', this is a democratically elected government,” Yingluck told reporters outside parliament, where she is being grilled by opposition lawmakers in a two-day confidence debate.

The anti-government campaign started last month after Yingluck's ruling Puea Thai Party tried to pass an amnesty bill that critics said was designed to absolve Thaksin of his graft 2008 conviction.

Thailand's Senate rejected the bill, but that did nothing to defuse the crisis.

“We will ask civil servants to join the people, to stop working for the Thaksin system. We don't want any confrontation,” Akanat Promphan, a spokesman for the protesters and Suthep's stepson, told Reuters.

More ministries under threat

Thailand's Department of Special Investigation is being evacuated, its director said, after at least 1,000 protesters surrounded the building on Wednesday in an attempt to shut down key government buildings and ministries.

The department, Thailand's equivalent of the Federal Bureau of Investigation in the US, is one of several state targets of demonstrators seeking to topple Prime Minister Yingluck Shinawatra's government.

Its offices form part of a complex of government departments, including those handling tax, immigration and land.

“We have ordered the evacuation of the DSI building,” Tharit Pengdit told Reuters.

“All our employees will be out within half an hour.”

The DSI recently indicted protest leader Suthep Thaugsubanfor his alleged role, while serving as deputy prime minister, in the deaths of more than 90 people in a 2010 military crack down on supporters of former Thai premier Thaksin Shinawatra,Yingluck's brother.