BANGKOK (AFP) - Fresh skirmishes broke out on Monday between Thai security forces and opposition demonstrators who have issued an ultimatum for Prime Minister Yingluck Shinawatra to quit, a day after the anti-government campaign erupted into deadly violence.
Police used tear gas at the heavily guarded government headquarters, as protesters hurled sticks and other projectiles at security forces manning barriers at the besieged complex.
Some schools and universities in the capital were closed for safety reasons, authorities said, after unrest on Sunday rippled around the key government buildings in the capital that have been targeted.
The protests, aimed at unseating the elected government and replacing it with a "people's council", are the latest outbreak of civil strife to rock the kingdom since royalist generals ousted Mr Thaksin Shinawatra, Ms Yingluck's brother, seven years ago.
The billionaire tycoon-turned-premier is hated by the elites, Bangkok's middle class and southerners, who have massed in the capital in recent days vowing to rid the country of his influence.
But he is adored by many outside Bangkok, particularly in his stronghold in the nation's north, and Ms Yingluck's party has a solid parliamentary majority.
Protest leader Suthep Thaugsuban said late Sunday that he had met Ms Yingluck in secret in the presence of army, navy and air force commanders, but insisted the talks were simply a means to issue his demand for the government to hand power "to the people".
"There will be no bargaining and it must be finished in two days," he said in a televised speech.
The month-long street rallies are the biggest since mass pro-Thaksin protests in Bangkok three years ago that left dozens dead and ended in a bloody military crackdown.
Police said an estimated 70,000 people joined the opposition demonstration on Sunday.
While the protesters' numbers have fallen since an estimated 180,000 people joined an opposition rally on November 24, they have besieged high-profile targets including ministries in what some observers believe is an attempt to provoke a military coup.
Police on Sunday repeatedly fired tear gas and water cannon as a hard core of protesters tried for hours to breach barricades and cut barbed wire protecting Government House, which was guarded by security forces including unarmed soldiers.
Mr Suthep said the demonstrators would not be satisfied with new elections, raising fears of a deepening crisis that could scare off foreign tourists and international investment in one of Southeast Asia's most vibrant economies.
In a televised press conference on Sunday, deputy prime minister Pracha Promnog insisted the government was in control. He accused Suthep of seeking "to overthrow the executive branch, which is treason and punishable by death".
The weekend's violence broke out on Saturday near a suburban stadium where tens of thousands of pro-government "Red Shirts" had gathered in support of Ms Yingluck.
Several were killed and dozens wounded, according to Bangkok's Erawan emergency centre. The dead and injured suffered a range of wounds including gunshots and stabbings. At least two of the dead were believed to be Red Shirt supporters.
The circumstances of the violence were unclear but the trouble came after an anti-government mob attacked Red Shirts arriving to join the rally in Ramkhamhaeng district.
They were the first deaths since the mostly peaceful demonstrations began a month ago. Both sides blamed each other for attacking their supporters.
Mr Suthep urged civil servants nationwide to go on strike on Monday although it was unclear how many would heed his call, which was rejected by the government.
Thailand has seen 18 actual or attempted coups since 1932, most recently with Mr Thaksin's overthrow in 2006, but the military has appeared reluctant to intervene in the current standoff.
The authorities have deployed more than 2,700 troops to reinforce security in Bangkok, the first time a significant number of soldiers has been mobilised to cope with the recent unrest.
The protests were triggered by an amnesty bill, since abandoned by the ruling party, which opponents feared would have allowed Mr Thaksin to return to the country.