Confrontation between protesters and police in the Thai capital Bangkok continues after several rounds of teargas are fired by riot police. Reuters

Police in Bangkok have fired teargas at thousands of anti-government protestors calling for the overthrow of the Thai government.

At least 9,000 people attended the rally, organised by activists who believe the current prime minister, Yingluck Shinawatra, is the puppet of her brother, the deposed former PM Thaksin Shinawatra.

Around 17,000 riot police were deployed to contain the protest, with officers firing tear gas at demonstrators who tried to climb over concrete and barbed wire barriers blocking entry to the rally site, Bangkok's Royal Plaza, near the parliament.

The rally was organised by the royalist Pitak Siam group, led by retired military general Boonlert Kaewprasit, which accuses Yingluck's government of corruption.

The group is supported by the 'yellow shirts' of the People's Alliance for Democracy, who have been involved in destabilising or ousting governments led or backed by Thaksin in 2006 and 2008.

Boonlert told supporters: "The world will see this corrupted and cruel government. The world can see the government under a puppet."

A police spokesman said five officers had been injured in the skirmishes, two of them seriously, and that 130 demonstrators had been detained, some of them carrying knives and bullets.

At clashes near the UN Asia-Pacific headquarters, near the site of the main rally, least seven police were wounded and up to 132 protesters arrested.

Yingluck's government has invoked the Internal Security Act, which gives police powers to detain protesters, to carry out security checks, and to set up roadblocks.

The demonstration reflects the tensions that have destabilised the country since the army ousted Thaksin Shinawatra in military coup in 2006. Thaksin fled the country in 2008, shortly before being found guilty of abuse of power.

Thitinan Pongsudhirak, a political analyst at Chulalongkorn University in Bangkok, said the government's action against the protesters was heavy-handed and could prove counter-productive.

He said: "At this stage, the government is more a threat to itself. If it overreacts using an army of policemen that's going to enrage demonstrators and things could get out of control."

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

Yingluck was elected after a landslide victory in August 2011. She was initially criticised for her lack of political experience but has won praise for leading the country through one of its longest peaceful periods in recent years.