Conflict in Thailand
Conflict in ThailandReuters

The Thai army said Monday night that it is imposing martial law amid a political crisis "to preserve law and order.” The surprise announcement also granted the army wide-ranging powers to enforce its decision. It follows six months of violent unrest and anti-government demonstrations and comes one day after the country's caretaker prime minister refused to step down.

The military insisted that it was assuming responsibility for national security but that the move is not a coup. The United States issued a statement in which it said that the military's assumption of power must be temporary and not undermine democracy.

The chief security advisor to the interim prime minister in Thailand said the government had not been consulted about the army's decision.

The move, which came as a surprise, was announced on the military's television channel and sparked fears that the move was part of a coup d'etat.

Thailand's army has staged 11 successful coups since the end of absolute monarchy in 1932. Soldiers reportedly entered several private television stations that are sympathetic to protesters. A ticker on Channel 5, an army station, however, denied the military was taking over, saying "the invocation of martial law is not a coup."

Soldiers also reportedly encircled a pro-government redshirt protest in Thailand's capital, the rally leader said, after the declaration of martial law. "The military is negotiating with the Red Shirts to disperse," he said. The Red Shirts were angered by the dismissal of prime minister Yingluck Shinawatra earlier this month in a controversial court ruling and have threatened civil war.

A military crackdown on Red Shirts protests in 2010 under the previous government left dozens dead.

The United States is concerned about the political crisis in Thailand and urges "all parties to respect democratic principles, including respect for freedom of speech," State Department spokeswoman Jen Psaki said in a statement.

"We understand the Royal Thai Army announced that this martial law declaration is not a coup. We expect the Army to honor its commitment to make this a temporary action to prevent violence, and to not undermine democratic institutions," Psaki said.

"The United States firmly believes all parties must work together to resolve differences through dialogue and find a way forward. This development underscores the need for elections to determine the will of the Thai people," she added.

Violence in recent months follow eight years of upheaval that has pitted the largely rural supporters of former Prime Minister Thaksin Shinawatra against the Southeast Asian nation's traditional elites.