Gunshots were fired and an anti-government crowd attacked motorcyclists and vehicles near a stadium rally by supporters of Thai Prime Minister Yingluck Shinawatra yesterday, as tensions boiled over amid attempts to topple her from power.

Several people were wounded when shots were fired as chaos erupted in Bangkok’s Ramkamhaeng area, where protesters armed with sticks attacked a bus and taxi and badly beat two people, police and Reuters witnesses said.

The US Embassy in Bangkok expressed concern about the rising political tension. It was unclear who had fired the shots and how many people were injured, Adul Saengsingkaew, national police commissioner-general, told Reuters.

With a deadline set for today by demonstrators for the ousting of the government, police called for military backup to protect Parliament and Yingluck’s office, Government House, where protesters tore down stone and razor wire barriers ahead of a planned move to occupy it.

Demonstrators have started to up the ante and briefly occupied the headquarters of the army on Friday, urging it to join them in a complex power struggle centred on the enduring political influence of Yingluck’s billionaire brother, ousted Prime Minister Thaksin Shinawatra.

Those attacked by the crowd were accused of being ‘red shirts’, ardently loyal supporters of Yingluck and Thaksin, who gathered in their thousands at the Rajamangala stadium to ward of any coup attempt against the government.

The tension heightens a nearly decade-long conflict that broadly pits Thailand’s traditional establishment of top generals, royalists and the urban middle class against the mostly rural, northern supporters of Thaksin.

Protest leader Suthep Thaugsuban told supporters late on Friday to surround the headquarters of the national and city police, along with Government House and even a zoo today.

“We need to break the law a little bit to achieve our goals,” said Suthep, a deputy prime minister in the previous government, routed by Yingluck in a 2011 election.