BANGKOK, Thailand -- A leader of a pro-government movement backing Thailand's beleaguered prime minister has vowed to fight back if the country's judicial institutions and oversight agencies tried to remove the government undemocratically.

Red Shirt leader Jatuporn Promphan made the comments Saturday at the start of a three-day rally on the outskirts of Bangkok that is aimed at countering months of anti-government protests and a spate of legal challenges that could bring down Prime Minister Yingluck Shinawatra's administration.

"What we are most concerned about ... is a civil war, which we do not want to happen," Jatuporn told reporters. But, he added: "It will happen if there is a coup and democracy is stolen."

Although the number of anti-government protesters has dwindled dramatically in recent weeks, Yingluck and her government remain highly vulnerable to legal threats, which her supporters say have intensified since street protests failed to unseat her. Most analysts predict her administration will fall in a "judicial coup" because Thailand's courts and independent state agencies are widely seen as biased against the Shinawatra political machine.

Speaking to a crowd of tens of thousands, Jatuporn said protesters and the nation's judicial institutions were trying "to take over power without elections. .... We will fight if the country becomes undemocratic."

"The Thai people have reached the point of no hope, because we are now aware of the repeated deceptions," he said in comments to reporters afterward.

Thailand has been shaken by more than five months of anti-government protests that snowballed after the ruling party tried to ram an amnesty bill through Parliament that would have allowed Yingluck's brother Thaksin Shinawatra, a billionaire former prime minister who was overthrown by the army in a 2006 military coup, to return from self-imposed exile and avoid serving a jail sentence for corruption.

After Thaksin's ouster, two pro-Thaksin premiers were forced from office after controversial judicial rulings and parliamentary manoeuvring. The power struggle is now focused on removing Yingluck, who took office in 2011 after a landslide vote that was deemed free and fair. Two dozen people have been killed and more than 700 wounded in sporadic violence since November.

On Wednesday, the constitutional Court announced it will hear a case accusing Yingluck of misconduct for transferring her National Security Council chief in 2011 to another position in a conflict of interest. The court ordered Yingluck to present her defence within 15 days. If she is found guilty of interfering in state affairs for her personal benefit or that of her political party, she would have to step down.

Two days earlier in a separate case under consideration by the National Anti-Corruption Commission, Yingluck defended herself against charges of dereliction of duty in overseeing a contentious rice subsidy program. If that case goes forward, it could lead to her suspension and eventual impeachment by the Senate.

Yingluck is currently serving as a caretaker prime minister whose powers were automatically reduced when she called February elections, dissolving the lower house of Parliament. That move was meant to ease the political crisis, but it only intensified. Although elections were held, the poll was annulled last month by the constitutional Court.

No date has been set for a new vote, and Yingluck's opponents hope that a failure to form a new government will spark a constitutional crisis, allowing them to invoke vaguely defined clauses in the charter and have an unelected prime minister installed.

The Red Shirt rally has so far been peaceful. The last time the group gathered en masse in Bangkok, at a stadium in the in November, shooting broke out nearby and five people were killed.

The Red Shirts have avoided rallying in Bangkok since then to avert bloodshed, and the current three-day gathering is being held dozens of kilometres (miles) from downtown Bangkok, on the western edge of the sprawling metropolis, for the same reason.