BHOPAL , India - Police arrested more than 150 people and deployed hundreds of armed guards at the Union Carbide plant today to prevent violence on the anniversary of the gas leak that killed more than 2,000 people.

Security also was tightened at all 12 Union Carbide plants in India, said Vijay P. Gokhale, managing director of Union Carbide's Indian subsidiary. A metal barricade was erected at the Bhopal plant to prevent its gate from being crashed.

No violence was reported at any of the plants.

Protesters planned torchlight marches to the Bhopal Union Carbide factory to demand that the company be expelled from India, and to mourn victims of the world's worst industrial disaster.

On Tuesday, they planned to burn more than 2,000 effigies of Union Carbide chairman Warren Anderson.

Reinforcements were rushed to this central Indian city to aid local and state police in the event the protests turned violent, the Madhya Pradesh state police director, B.K. Mukherjee, said. Police said the 150 people arrested were "anti-social elements" who had been rounded in an effort to prevent violence.

"People are still scared of what is inside the factory," said Sadhna Karnik, 27, who works with gas victims. "They say Union Carbide should be punished and every nail of this factory dismantled and sold."

"Although it is one year after the gas leak, the government has failed on every front," added Karnik, a leader of a group called the Poison Gas Episode Struggle Front. "They are in league with Carbide and trying to hide facts."

Social activists have charged that the government and Union Carbide are withholding information on extent and severity of injuries while trying to reach an out-of-court settlement.

The Madhya Pradesh state government ordered schools and government offices closed today and Tuesday as "prayer days" in memory of the slum dwellers killed by the cloud of toxic gas that escaped from Union Carbide's pesticide plant.

More than 300,000 people were injured by fumes that wafted over the shanty towns surrounding the plant late on the night of Dec. 2 and early in the morning of Dec. 3 , 1984.

The state chief minister, Motilal Vora, was scheduled to distribute the first installment of a 200 rupee, or $16, monthly pension to 2,842 women widowed by the disaster.

Vora, the state's top elected official, branded Union Carbide as "unscrupulous death dealers" and charging that the company acted with a "disregard for human life unparalleled in human history."

He said Anderson was spreading "disinformation" by alleging in a recent interview with an American newspaper that Sikh extremists probably sabotaged the plant. Sikh radicals are waging a terror campaign for greater autonomy or independence in Punjab.

Last week the state government accused the U.S. multinational, before a judicial commission, of negligence and responsibility for the leak. It said the plant was badly designed, defective and unsafe.

India's central Bureau of Investigation will file criminal charges against Anderson and top officials of the company's Indian subsidiary in the next few weeks, United News of India reported today.

Anderson and two officials of the Indian subsidiary were detained by police on Dec. 7 on preliminary charges of negligence and criminal corporate liability. But they were released within hours and no formal charges were filed.

The company denied the allegations, saying the plant was well-designed, safe, and routinely inspected by Indian agencies that never found "any significant fault."

Union Carbide questioned why Indian authorities allowed squatters to settle next to the plant in slums encroaching on land designated only for industry.

A team of Indian scientists reported Sunday they still do not know the exact nature of the poison gas or its components.