BANGKOK, Thailand — Thailand’s prime minister declared a state of emergency in the capital today after street fighting overnight between supporters and opponents of the government left one man dead and dozens injured.

The developments followed a threat by state workers to cut off water, electricity, and phone service at government offices and disrupt flights of the national airline in support of protesters trying to bring down Prime Minister Sundaravej.

An announcement broadcast on all Thai television stations at 7 a.m. said Mr. Samak had decreed a state of emergency in Bangkok and Army General Anupong Paochinda was in charge of enforcing it.

In Thailand, a state of emergency allows the use of military forces in policing activities, and suspends some civil liberties.

A week of political tension exploded into violence early this morning between protesters seeking to topple Mr. Samak and mobs of his supporters.

About 500 Samak supporters marched through the streets proclaiming they were going to retake the prime minister’s office compound, which has been occupied since August 26 by the People’s Alliance for Democracy.

The mob scuffled with police about halfway to the Government House complex, then battled with alliance members, both sides wielding sticks and clubs.

Police were unable to stop the fighting, which eased up only after army troops with riot gear — but no guns — reached the scene.

Although the troops were able to keep the antagonists apart, few supporters of either side dispersed, keeping the area a flashpoint for further trouble.

One person died from severe head injuries and four others were in serious condition, two with gunshot wounds, Dr. Petchapon Kumtonkitjakarn of the Erawan Medical Center told the Associated Press. He said 37 people were being treated for injuries at several hospitals.

Yesterday, a coalition of 43 unions representing workers at state companies including water, electric, phone, and the national airline said they would cut off services to the government starting tomorrow in support of the anti-government protests. They already were disrupting rail service and planned to cut back public bus transportation.

“The government has beaten protesters, and that justifies our retaliating by stopping water, telephone service, and electricity to some government agencies,” the secretary-general of the State Enterprise Workers Relations Confederation, Sawit Kaewwan, said at a news conference.

The labor federation said 200,000 members would stop work in support of the alliance of right-wing protesters that has occupied Mr. Samak’s office for a week in its campaign to bring down the government.

The alliance claims the government is corrupt and too close to Prime Minister Shinawatra, who was ousted in a 2006 military coup and recently fled to Britain to escape an array of corruption charges. The same group organized the massive anti-Thaksin demonstrations in 2006 that helped spark the bloodless coup.

The alliance and their sympathizers — monarchists, the military, and the urban elite — complain that Western-style democracy with one-man, one-vote gives too much weight to Thailand’s rural majority, who protesters say are susceptible to vote buying that breeds corruption. They have proposed a system under which most lawmakers would be appointed rather than elected.

The prime minister has repeatedly insisted he will not bow to pressure by resigning or dissolving parliament to call new elections.

“I am sure that I love this country as much as anybody,” Mr. Samak said at a joint session of the upper and lower houses of parliament convened to debate solutions to the deadlock. “But I love democracy much more, more than anyone who told me to resign.”

Mr. Sawit and others laid out plans for the work stoppage by state employees but did not say how long the action would last.

Public bus workers will halt service on 80% of Bangkok’s 3,800 buses, with the remainder running for free, he said.

Workers for state-owned Thai Airways plan to delay flights tomorrow, the deputy chief of Thai Airways International labor union, Somsak Manop, said.