Thailand protests: Teargas fired amid renewed clashes
Thai authorities fired tear gas amid renewed skirmishes with anti-government protesters outside key government buildings.
Some schools and universities closed, amid a call for a general strike on the ninth day of demonstrations.
Over the weekend, protesters attempted to storm the prime minister's office, Government House.
Four people have died in Thailand's worst political turmoil since the 2010 rallies that ended in violence.
The protesters, who want Prime Minister Yingluck Shinawatra to step down, had declared Sunday the decisive "V-Day" of what they termed a "people's coup".
However, despite clashing with security forces, they failed to seize more government buildings or unseat Ms Yingluck.
On Monday, some protesters returned to barricades outside official buildings in the capital, Bangkok.
Correspondents say that demonstrator numbers appear lower than before. A hard core of protesters are still pushing at police barricades but seem to be unable to break through, they add.
Skirmishes have broken out, with reports of stones and homemade explosives being thrown by protesters, and tear gas and rubber bullets being used by police.
Several schools and universities have closed, citing security concerns. AP news agency reported that 60 schools in Bangkok, as well as the main UN office, were shut.
In a televised appeal, Ms Yingluck's deputy, Surapong Tovichakchaikul, said the government would like to "lead Thailand back to peace soon".
The government would "exercise utmost patience and adhere to nonviolent principles," he added.
The protests had been largely peaceful until the weekend, when the unrest escalated.
Protesters entered TV stations to ensure a message from leader Suthep Thaugsuban was aired, and tried to break into a Bangkok police complex where Ms Yingluck had intended to give interviews, forcing her evacuation.
On Sunday, Mr Suthep, a former opposition party politician, said he had met Ms Yingluck and given her a two-day deadline to resign.
"I told Yingluck that this is the only and last time I see her until power is handed over to the people," he was quoted as saying.
"There will be no bargaining and it must be finished in two days."
He also called on civil servants to "stop working for the Thaksin regime and come out and protest" on Monday.
However, Reuters news agency reported that government offices remained open on Monday, with many civil servants going to work as usual.
Major shopping malls also said they had reopened, the Bangkok Post reported.
Deputy Prime Minister Pracha Promnok said on Sunday that Mr Suthep was seeking "to overthrow the executive branch, which is treason and punishable by death," AFP news agency reported.
Ms Yingluck's government, which has broad support outside the capital, took office after winning elections in 2011.
However, protesters say her administration is controlled by her brother, exiled ex-leader Thaksin Shinawatra. They want to replace her government with a "People's Council" instead.
On Friday Ms Yingluck ruled out early elections, telling the BBC that the country was not calm enough for polls. She repeated her call for negotiations to resolve the crisis.
Thailand is facing its largest protests since 2010, when thousands of red-shirt Thaksin supporters occupied key parts of the capital.
More than 90 people, mostly civilian protesters, died over the course of the two-month sit-in.