This is not a war on terror. It is a racist war on all Tamils

The horror that is unfolding in Sri Lanka becomes possible because of the silence that surrounds it. There is almost no reporting in the mainstream Indian media - or indeed in the international press - about what is happening there. Why this should be so is a matter of serious concern.

From the little information that is filtering through, it looks as though the Sri Lankan government is using the propaganda of "the war on terror" as a fig leaf to dismantle any semblance of democracy in the country, and commit unspeakable crimes against the Tamil people. Working on the principle that every Tamil is a terrorist unless he or she can prove otherwise, civilian areas, hospitals and shelters are being bombed and turned into a war zone. Reliable estimates put the number of civilians trapped at over 200,000. The Sri Lankan army is advancing, armed with tanks and aircraft.

Meanwhile, there are official reports that several "welfare villages" have been established to house displaced Tamils in Vavuniya and Mannar districts. According to a report in the Daily Telegraph, these villages "will be compulsory holding centres for all civilians fleeing the fighting". Is this a euphemism for concentration camps? Mangala Samaraveera, the former foreign minister, told the Telegraph: "A few months ago the government started registering all Tamils in Colombo on the grounds that they could be a security threat, but this could be exploited for other purposes, like the Nazis in the 1930s. They're basically going to label the whole civilian Tamil population as potential terrorists."

Given its stated objective of "wiping out" the Liberation Tigers of Tamil Eelam, this malevolent collapse of civilians and "terrorists" does seem to signal that the government of Sri Lanka is on the verge of committing what could end up being genocide. According to a UN estimate, several thousand people have already been killed. Thousands more are critically wounded. The few eyewitness reports that have come out are descriptions of a nightmare from hell.

What we are witnessing, or should we say what is happening, in Sri Lanka - and what is being so effectively hidden from public scrutiny - is a brazen, openly racist war. The impunity with which the Sri Lankan government is being able to commit these crimes actually unveils the deeply ingrained racist prejudice that is precisely what led to the marginalisation and alienation of the Tamils of Sri Lanka in the first place. That racism has a long history - of social ostracism, economic blockades, pogroms and torture. The brutal nature of the decades-long civil war, which started as a peaceful protest, has its roots in this.

Why the silence? In another interview Samaraveera says that "a free media is virtually non-existent in Sri Lanka today". He talks about death squads and "white van abductions", which have made society "freeze with fear". Voices of dissent, including several journalists, have been abducted and assassinated. The International Federation of Journalists accuses the Sri Lanka government of using a combination of anti-terrorism laws, disappearances and assassinations to silence journalists.

There are disturbing but unconfirmed reports that India is lending material and logistical support to the Sri Lankan government in these crimes against humanity. If the reports are true, it is outrageous. What of the governments of other countries? Pakistan? China? What are they doing to help or to harm the situation?

In the Indian state of Tamil Nadu the war in Sri Lanka has fuelled passions that have led to more than 10 people immolating themselves. The public anger and anguish, much of it genuine, some of it cynical political manipulation, has become an election issue.

It is extraordinary that this concern has not travelled to the rest of India. Why is there silence here? There are no "white van abductions" - at least not on this issue. Given the scale of what is happening in Sri Lanka, the silence is inexcusable. More so because of the Indian government's long history of irresponsible dabbling in the conflict, first taking one side and then the other. Several of us - including myself - who should have spoken out much earlier have not done so, simply because of a lack of information about the war.

So while the killing continues, while tens of thousands of people are being barricaded into concentration camps, while more than 200,000 face starvation, and a genocide waits to happen, there is dead silence from this great country.

It's a colossal humanitarian tragedy. The world must step in. Now. Before it's too late.

Arundhati Roy, a writer and activist who won the Booker Prize for her novel, The God of Small Things.