By Jyotsna Singh BBC correspondent in Bhopal

There has been widespread anger at the treatment of the Bhopal victims

Almost 2,000 people died instantly when tonnes of the paralytic methyl isocyanate gas leaked from a pesticide plant in Bhopal, central India, in the early hours of the morning on 3 December, 1984.

The plant was owned at the time by the US company, Union Carbide.

The story of the gas victims, say rights groups, has been one of callous delays and wrangling between Indian and US courts over damages and medical care.

Earlier this year, a US court rejected a compensation claim against Union Carbide, saying the company had fulfilled its duty to clean up the site.

Union Carbide has accepted moral responsibility for the disaster and paid out $470m in compensation in an out-of-court settlement in 1989.

Promises not kept

In the narrow alleyways of the shanty town near the plant, where thousands of the gas victims still live, is the house of Raisa Bi.

Raisa Bi barely has enough money to cook for her ailing husband

She has been struggling to provide medicines for her ailing husband, who suffers from acute stomach pain and breathlessness.

Life has never been the same for Raisa and thousands of others in her neighbourhood since the gas disaster struck.

The worries over proper medical care for her husband are compounded by the dire financial state Raisa finds herself in.

She earns less than $2 a week from sewing work provided by a local non-government organisation (NGO), Swabhiman (Self-pride).

It is barely enough to pay for food for both of them.

"I don't have the documents to prove that I am poor, so I can't get any benefits from the government. Nobody was given any jobs.

The growing international voice may finally force the governments and the company to act for the victims Satinath Sarangi, NGO worker

"It has been 20 years since the promises were made! I haven't had a life. We have been left to God's mercy," Raisa told the BBC.

Nagma, aged 19, earns a living for her disabled parents and brother by making paper bags.

She was one year old on that fateful morning in 1984.

"We have little hope," she says.

'Callous' approach

Nearly 20,000 people have died of various diseases since the disaster, which injured nearly 100,000 people.

Almost half of the survivors were left totally or partially disabled.

It has been a tough battle getting help for the survivors of one of the world's worst industrial disasters, as courts in the US and India argue over damages, medical costs and compensation.

The shantytown near the chemical plant still bears the scars of 1984

The Indian Supreme Court was asked to intervene after a dispute between the state and national governments over the legal right to disburse nearly 1.5 billion rupees (about $33m) in compensation, paid by Union Carbide which was later taken over by another company, Dow Chemicals.

The NGOs working in the area describe the attitude of the governments as "simply callous".

They have appealed to the governments to act urgently on issues such as providing free medical care, employment and most importantly, safe drinking water.

"It has been scientifically proven that water from nearly 100 hand-pumps in the area is unsafe," says Abdul Jabbar, a gas victim himself, whose Swabhiman organisation provides small, casual jobs for gas survivors.

"But none of the governments are taking it seriously," he says.

Mounting concern

NGOs are also demanding medical research into the after-effects of the gas leak.

"Women are suffering from early menopause at 30 to 35 years," says Satinath Sarangi, who heads an NGO, Sambhavna (Brotherhood), involved in providing medical help to the victims.

"Cancer and TB cases are four times higher among people living in the gas-affected area," he said.

Activists in Bhopal protest against the lack of relief for victims

"Many gas victims' babies have been born with deformities. Why is there no research to help a more systemic approach in dealing with these cases?" asks Mr Sarangi.

Between Tuesday and Wednesday student groups and activists all over the world will hold midnight vigils and demonstrations demanding that Indian and state governments, as well as Dow Chemicals, take full responsibility for the rehabilitation of the Bhopal victims.

Human rights activists see hope in the mounting international concern for the victims.

French writer Dominique Lapierre donates the proceeds of his book on Bhopal to help gas victims.

Over the last two years, Greenpeace activists have also held several protest demonstrations attacking government inaction.

"Thousands of students from the US, European Union, Britain, Japan and many other countries have sent us letters of solidarity and support," says Mr Sarangi.

"The growing international voice may finally force the governments and the company to act for the victims."