BANGKOK - Tensions escalated in the Thai capital on Saturday as opposition protesters tried to force their way into Prime Minister Yingluck Shinawatra's heavily guarded offices and attacked a bus carrying her supporters.
Defiant demonstrators seeking to topple Yingluck's embattled administration have besieged major state buildings in Bangkok in the biggest street protests since mass rallies in 2010 left dozens dead in a military crackdown.
The protesters - a mix of royalists, southerners and the urban middle class sometimes numbering in their tens of thousands - are united by their loathing of ousted former premier Thaksin Shinawatra, Yingluck's older brother.
They are demanding the end of the "Thaksin regime" and want an unelected "people's council" to replace the government, in a country that has suffered years of political turmoil.
While their numbers have fallen sharply since an estimated crowd of up to 180,000 people joined an opposition rally on November 24, the protesters have increasingly sought out high profile targets.
Vowing a final push to achieve victory, opposition protesters used piles of sandbags to try to climb over barriers protecting Government House.
"About 2,000 protesters of students network were trying to pressure the police" said National Police spokesman Piya Utayo, adding that demonstrators were believed to be bringing more sandbags to key locations.
"We have information that there will be efforts to escalate violence in several areas," he added.
Yingluck was not believed to be at Government House at the time.
At the same time a mob of opposition demonstrators also attacked a bus carrying "Red Shirt" government supporters heading to their own rally at a sports stadium on the other side of Bangkok, throwing paving stones and other objects, according to an AFP photographer at the scene.
Piya said police closed a nearby road to try to prevent further confrontations between the protesters and Red Shirts, who have massed in their tens of thousands.
But demo organisers are urging people to turn out in strength this weekend in a final push before celebrations for revered King Bhumibol Adulyadej's birthday on December 5, which is traditionally marked in an atmosphere of calm and respect.
Thaksin, a former telecoms tycoon, was ousted in a military coup in 2006 and lives in self-imposed exile, but he is widely believed to be the real power behind the embattled government of his younger sister Yingluck.
Pro-Thaksin Red Shirts, who have gathered in a stadium in Bangkok for a week, began stepping up their demonstrations Saturday, with tens of thousands expected at the site, vowing to protect the government.