Thousands of protesters called for the overthrow of the Thai government on Saturday and demanded an end to "corrupt politics" in the first major demonstration against prime minister Yingluck Shinawatra's administration since it assumed power last year.

While many of the 10,000 protestors gathered peacefully around a stage set up near the Royal plaza in Bangkok, others repeatedly tried and failed to charge past concrete police barricades and, at one point, attempted to drive a truck straight into the barricades as well.

Protesters and riot police were seen throwing tear gas back and forth at one another in sometimes fierce standoff. Five officers were hurt, two of them seriously, and 130 protestors were detained by the rally's end at dusk. Around 45 protestors were treated in hospital, mainly for tear gas inhalation.

Saturday's rally was organised by a pro-monarchy group called "Patik Siam" (Protect Thailand), led by retired army general Boonlert Kaewprasit, which denounces Yingluck's government as a corrupt puppet administration of her brother, former prime minister Thaksin Shinawatra.

From the central stage that faced the parliament building, Boonlert incited chants of "Yingluck, get out!" and told protestors: "I promise that Pitak Siam will succeed in driving this government out."

Thaksin's own administration was deposed in a 2006 army coup after rallies by the pro-monarchy "yellow shirt" movement ousted his administration. Four years later, mass protests led by pro-Thaksin supporters led to two months of violent political turmoil that saw around 2,000 wounded and 90 people killed in brutal clashes with security forces.

While Yingluck won by a landslide in 2011 elections, simmering political tensions still run high. Pitak Siam is a new group in Thailand's protest scene, and is linked to the yellow-shirt movement – although it does not yet seem to be as popular as its leaders would like.

Various rumours circulated ahead of Saturday's rally, among them a threat that Yingluck would be taken hostage and that as many as a million protestors would take to the streets to call for her resignation. Citing safety concerns, the government deployed some 17,000 police and invoked an internal security act that allowed for road closures, curfews and the ban of electronic devices in certain areas.

Analysts said the protest did not seem an immediate threat to Yingluck's administration, but that it proved a thorn in the stability of Thai politics. "Any time you have tens of thousands of people converging, assembling in a central Bangkok location, it becomes a government stability concern," said Thitinan Pongsudhirak, a political scientist at Bangkok's Chulalongkorn University.

But he added: "I think it's a serious concern more than a serious threat."

Many protestors at Saturday's rally seemed unhappy with the current government but were unable to state what exactly they would prefer in its place.

"Yingluck is a very good businesswoman, but she has no political experience – and this is an embarrassment to us Thais," explained protestor Pathinan, 39, a pharmacist from Bangkok. "We should at least have someone governing us who has done the job before, not just someone who does what her brother tells her to do. But who should be in her place? I don't know."