Deputy Prime Minister Surapong Tovichakchaikul said during a news conference the state of emergency goes into effect Wednesday and will be imposed throughout the capital, Nonthaburi province and some districts in other provinces nearby, the Wall Street Journal reported.
Surapong said the government's goals are to enforce laws regarding the protests and supporters of the movement to oust Prime Minister Yingluck Shinawatra and limit "the spread of distorted information that incites chaos and division, which affects the country's security."
Protesters have erected barricades to block streets leading to government offices to try to disrupt government operations and discourage government employees from going to work.
Thai authorities said they would reveal security measures Wednesday. Generally, emergency decrees give security authorities powers to hold suspects without charge, censor media, impose curfews and ban political gatherings greater than a certain number of people.
Since the anti-government protests erupted in November, nine people have been killed and dozens injured in clashes between rival protesters, security forces and attacks.
The escalation of violence raised fears of more unrest in the run-up to Thailand's elections Feb. 2, the Journal said. Protesters have said they want to foil the elections, expected to be carried by the prime minister's Pheu Thai Party.
Thailand's army says its intelligence found weapons smuggled into Bangkok, raising concerns of more violence as anti-government protests rage.
"An ill-intentioned group is mobilizing weapons and bombs to stir up violence and attack its rivals," the Bangkok Post quoted army spokesman Winthai Suwaree as saying.
The spokesman did not identify any group or give details of who the target might be, but the Post said the army is on alert in case of more violence.
The protesters blame the government and the red-shirt United Front for Democracy Against Dictatorship for the recent attacks, but supporters of the government -- including those clad in red shirts -- claim the protesters and military officers are responsible for fomenting anti-government sentiment, the Post said.
Yingluck has said the elections would be held as scheduled and the best way to remove her from office would be to vote. But the main opposition Democrat Party and the protesting PDRC plan to boycott the election.
The protesters oppose the election being overseen by Yingluck's government, demanding that it be conducted by a "people's council." They maintain her government is corrupt and is controlled by her brother Thaksin Shinawatra -- a former prime minister and a telecommunications billionaire who has lived in exile since his ouster in a 2006 coup. The government denies the allegations.