Thailand’s beleaguered government moved to shut down media outlets of anti-government demonstrators on Thursday after declaring a state of emergency, while the activists vowed to escalate their protests if an information blackout is enforced.

The defiant “Red Shirts” have controlled areas of the Thai capital for nearly a month in efforts to get Prime Minister Abhisit Vejjajiva to dissolve parliament, and they planned another mass rally on Friday despite the emergency order that empowers the military to move against large gatherings.

Mr. Abhisit cancelled a trip to Hanoi on Thursday to attend a summit of Southeast Asian leaders as he groped for ways to resolve the crisis without use of armed force.

Government spokesman Panitan Wattanayagorn said the government has shut down PTV, the satellite TV station of the Red Shirts, and is looking for Web sites disseminating “distorted information” such as claiming that Mr. Abhisit authorized the use of force against demonstrators.

“We aim to control the broadcasting of certain media, including TV stations and others. It is very clear that some of the media broadcasts have been destructive to the stability of the country,” he told reporters.

A protest leader, Nattawut Saikua, told followers that a media blackout “is just the first step for the government to clamp down on us tomorrow morning. If this is so, we’re going to raise our protest to the maximum level.”

Mr. Abhisit declared the emergency on Wednesday night after protesters briefly broke into Parliament, following weeks of protests that have paralyzed the government and cost businesses tens of millions of dollars. Lawmakers were forced to flee on ladders over a back wall and senior officials were hastily evacuated by helicopter.

The demonstrators championing the rights of the rural poor appear uncowed. Their makeshift camps that were set up in Bangkok’s historic district March 12 have spread to the main commercial district and beyond, forcing large shopping malls to close and luxury hotels to be put under virtual siege.

The confrontation is part of a long-running battle between supporters of former Prime Minister Thaksin Shinawatra, ousted by a 2006 military coup, and those who oppose him. Mr. Thaksin was accused of corruption and showing disrespect to the country’s revered monarch.

The demonstrators, called the Red Shirts for their attire, benefited from Mr. Thaksin’s populist policies such as cheap health care and village loans. They are demanding that Mr. Abhisit dissolve Parliament within 15 days and call new elections, claiming he took office illegitimately in December 2008 with the help of military pressure on Parliament.

Instead, the prime minister has offered to do so by the end of the year.

Protesters camped in the city have ignored court orders and a massive security presence. They have shown surprising tenacity as well as organizational skills, living under primitive conditions in scorching heat and moving around the city in well-ordered motorized columns.

Mr. Abhisit has been harshly criticized for failing to take strong measures to end the disruptive demonstrations. He has entered negotiations with the Red Shirts and ordered security forces to pull back from possible confrontations.

The emergency decree allows security officials to detain suspects without charge for up to 30 days and gives them the option of imposing curfews, banning public gatherings and censoring media.

Although the military now has greater power to restore order, both Mr. Abhisit and the army know a crackdown could result in bloodshed that would be political poison.

The media clampdown may also prove difficult, with Panitan acknowledging the protesters are trying to find ways to get around the blocks. PTV, set up and financed by Red Shirt sympathizers, is particularly important to the protesters as a means of communicating their aims and plans.

A number of small community radio stations are also allied with the protesters, who also use cell phones and social networking to communicate.

Most of Thailand’s television stations are owned by the government but the country’s many newspapers are privately owned and reflect a wide spectrum of political opinion.

Surat Horachaikul, a political science lecturer at Bangkok’s Chulalongkorn University, said the emergency announcement can be interpreted in two ways.

“First, it might be an attempt by the government to buy some time. Or it might actually mean that the government and the army have reached an agreement in solving the current problem,” he said.

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