The Thai army has moved hundreds of soldiers into the business district of Bangkok to prevent anti-government protesters entering the area.The protests by the "red-shirts", now in their fifth week, are currently focused in the city's shopping hub.
The red-shirts are trying to force Prime Minister Abhisit Vejjajiva to step down and call an election.
They had said they might move to Bangkok's financial district but later said they would not do so.
Government figures said the intent was not to attack the protesters, but simply to block any attempt they might make to enter the area.
Bank target
Late on Friday, Mr Abhisit put the army commander-in-chief, Anupong Paojinda, in charge of national security.
The general held a meeting of military commanders on Sunday, issued warnings to the red-shirt protesters to avoid the business district, and moved his troops into the area before dawn on Monday.
Soldiers are on patrol in the city's famous red light district of Patpong, and along Silom Road, where the headquarters of Bangkok Bank is located along with many other office buildings.
The bank is a target of the protesters' ire due to its establishment links. Head of the Privy Council and former prime minister Gen Prem Tinsulanonda is an adviser to the bank.
"There are several units currently armed to prevent themselves from attacks from terrorists who are hiding among protesters," said government spokesman Panitan Wattanayagorn.
The government uses the word "terrorist" to refer to an alleged militant hard-core of the anti-government movement, which has been largely peaceful.
Yellow threat
On Sunday, leaders of Thailand's yellow-shirt movement, which supports the political establishment, gave the government a week to end the red-shirts' protests or warned they would hold their own demonstrations.
The Peoples' Alliance for Democracy (PAD), the formal umbrella for the yellow-shirts, had last week called for martial law.
Some members had expressed frustration that the attempted military crackdown of 10 April failed to end the red-shirt protests. Twenty-five people were killed and more than 800 wounded.
The group has been largely silent since it closed down the country's airports in December 2008 and helped usher in the current government.
Other much smaller groups, claiming to be "no colour", have also held gatherings in recent days, calling for an end to the political confrontation.
Despite calls from some hard-line parts of the establishment, Gen Anupong has insisted on a political solution and said his troops were not planning further crackdowns.
The army plays a prominent role in Thai politics - former Prime Minister Thaksin Shinawatra was ousted by the military in 2006.
