"Thai security forces fired tear gas and rubber bullets at anti-government demonstrators Saturday, setting off fierce street battles during a large-scale crackdown aimed at ending a month of disruptive protests in the capital," the Associated Press reports from Bangkok. It adds that "more than 150 people have been injured, including some with gunshot wounds."
According to the BBC, "Thai troops are moving against two anti-government camps in the capital, Bangkok, vowing to clear at least one of them before dusk."
Canada's National Post has a primer on what the protests are all about. As the AP says:
"The so-called Red Shirt protesters are demanding that Prime Minister Abhisit Vejjajiva dissolve Parliament and call new elections. They claim that he came to power illegitimately in December 2008 with the help of military pressure on Parliament."