Twenty years after a cloud of deadly gas savaged this central Indian city, thousands of demonstrators and survivors marched through the streets on Friday, demanding justice for those still suffering the effects of the world's worst industrial disaster 20 years ago.

The crowds — spanning all ages of Indian society — shouted and waved signs as they walked through Bhopal's streets.

At least three protest rallies, organized by different groups of Bhopal (search) residents and aid groups working with disaster victims, were to converge outside the gates of the abandoned Union Carbide (search) pesticide plant later Friday.

A leak of 40 tons of poisonous gas from the pesticide plant on Dec. 3, 1984, killed at least 10,000 people in Bhopal and affected more than 555,000 others, although the exact number of victims has never been clear. Many died over the years due to gas-related illnesses, like lung cancer, kidney failure and liver disease.

"Don't forget the victims of the genocide in Bhopal!" and "Death to Dow!" the protesters shouted. Their banners carried similar slogans, accusing Union Carbide and Dow Chemical Co. (search) of inadequate compensation and medical help for the victims. Michigan-based Dow Chemical bought Union Carbide Corp. in 2001.

Another group of protesters staged a mock funeral procession for Warren Anderson (search), then-CEO of Union Carbide. A straw-filled effigy of Anderson was later set aflame.

While millions of dollars in compensation has been set aside, much of the money has been tied up by bureaucratic and legal issues and many people have received little or nothing.

"For the last 20 years I've been visiting the hospital and government offices, begging for compensation to take care of my two children," said Leelaben Aherwar, whose baby girl survived the gas leak but immediately afterward began showing signs of mental and physical retardation.

Her son, born a few years later, suffers from similar problems. "The answer is always the same: 'The court will make a decision.' I don't know what court is this that cannot see our suffering," she said Friday.

So far, she has received about $360.

Union Carbide paid $470 million in compensation under a settlement with India's government in 1989. But only part of that amount has reached the victims.

The protesters also called on Dow Chemical to clean up the plant site, where rusted pipes and pesticide storage tanks have collapsed or ruptured in the years since the plant was abandoned after the disaster.

"Lethal chemicals are still lying around at the plant, some in the open. Every time it rains these poisonous chemicals are leaked into the soil, affecting groundwater resources of the area," said Rashida Bee, a disaster survivor who heads a women victims' group.

Union Carbide insists the tragedy was due to sabotage by a disgruntled employee and not shoddy safety standards or faulty plant design, as claimed by many activists.

Union Carbide said in a statement that it spent more than $2 million to clean up the plant from 1985 to 1994, when it sold its stake in Union Carbide India Ltd. and the local company was renamed Eveready Industries.

The company also says state studies indicated in 1998 that the groundwater around the plant was free of toxins and that any water contamination was due to improper drainage and other pollution, not Union Carbide chemicals.

The state government took over legal responsibility of the site in 1998, but it has done little to remove the debris and sacks of chemicals. Greenpeace estimates it would cost at least $30 million to clean up the plant, groundwater and soil that it claims are laced with carcinogens.

Dow maintains the legal case was resolved in 1989, when Union Carbide settled with the Indian government.

Union Carbide claims that 3,800 people were killed, while Indian officials say up to 15,000 may have died.

Indian officials estimate that nearly 600,000 more have become ill or had babies born with defects over the last 20 years.