Weeks of protests have erupted into violence in the Thai capital as anti-government forces upped the ante in their campaign to bring down Prime Minister Yingluck Shinawatra's government.
A flurry of mob attacks - on a packed bus, a taxi and two people on a motorcycle - followed a call to occupy the Prime Minister's Office on Sunday. The targets were accused of being pro-government "red shirts".
The attacks raise fears for what might happen today as demonstrators vowed to carry out their final push to attain victory against what they call the "Thaksin regime" and install a "people's council" in its place.
The demonstrators seeking to topple Ms Yingluck's administration have already laid siege to major government buildings in Bangkok, in the biggest street rallies since the 2010 protests that left dozens dead.
A motley grouping of royalists and urban middle-class citizens, they are united by their hatred of ousted former prime minister Thaksin Shinawatra, the brother of the present Premier.
Security was beefed up around key government installations after protest leader Suthep Thaugsuban announced at the weekend plans to seize the Prime Minister's Office (PMO), national police headquarters as well as several key ministries on Sunday.
"We need to break the law a little bit to achieve our goals," he was quoted by Reuters as saying on Saturday.
Protesters have occupied the Finance Ministry since last Monday. on Saturday, thousands more marched from a multi-agency government complex on Bangkok's outskirts - part of which they are occupying - to two state-owned telecommunications units.
About 30,000 policemen are guarding the Government House - where the PMO is located - as well as Parliament, National Security Council chief Paradorn Pattanabutr told The Sunday Times. Another 15,000 have been deployed at key installations in the capital, alongside reams of barbed wire and concrete blocks designed to keep protesters away from no-go zones.
Thai police, haunted by memories of a bloody military crackdown on anti-government protesters in 2010 by the then Democrat government, have shown restraint, even after protesters cut the power supply to the national headquarters last Thursday.