West Pakistan's Army has been systematically massacring thousands of civilians in East Pakistan since the end of March. This is the horrifying reality behind the news blackout imposed by President Yahya Khan's government since the end of March. This is the reason why more than five million refugees have streamed out of East Pakistan into India, risking cholera and famine.

The curtain of silence is broken today for the first time by Anthony Mascarenhas, the Sunday Times correspondent in Pakistan. He has seen what the Pakistan army has been doing. He has left Pakistan to tell the world. The army has not merely been killing supporters of the idea of Bangla Desh an independent East Bengal. It has deliberately been massacring others, Hindus and Bengali Muslims. Hindus have been shot and beaten to death with clubs simply because they are Hindus. Villages have been burned.

Sporadic and unconfirmed reports of atrocities by the Pakistan army have been reaching the outside world for some time, notably from refugees, missionaries and diplomats. The report by Anthony Mascarenhas-appearing in full on pages twelve to fourteen today-is a detailed eyewitness account of unique precision and authority. He supplies the missing centre-piece of the tragedy of Bengal: why the refugees have fled.

There is a remarkable story behind Anthony Mascarenhas' report.

When, at the end of March, the Pakistan army flew two divisions into East Pakistan to "sort out" the Bengali rebels it moved in secret. But about two weeks later the Pakistan government invited eight Pakistani journalists to fly to East Bengal. The idea-as government officials left the journalists in no doubt- was to give the people of West Pakistan a reassuring picture of the "return to normalcy" in the eastern half of the country. Seven of the journalists have done as they were intended. But one was Mascarenhas, who is assistant editor of the Morning News in Karachi, and was also The Sunday Times Pakistan correspondent.

On Tuesday, May 18, he arrived, unexpectedly, in The Sunday Times office in London. There was, he told us. a story he wanted to write: the true story of what had happened in East Bengal to drive five million people to flight.

He made it plain that he understood that if he wrote his story there could be no going back to Karachi for him. He said he had made up his mind to leave Pakistan: to give up his house, most of his possessions and his job as one of the most respected journalists in the country. There was only one condition: we must not publish his story until he had gone back into Pakistan and brought out his wife and five children.

The Sunday Times agreed, and Mascarenhas went back to Karachi. After a wait of ten days an overseas cable arrived at the private address of a Sunday Times executive.

"Export formalities completed," it read, "Shipment begins Monday."

Mascarenhas had succeeded in getting permission for his wife and family to leave the country. He himself had been forbidden to leave. He found a way of leaving anyway.

On the last leg of his journey inside Pakistan, he found himself sitting in a plane across the aisle from a senior Ministry of Information official whom he knew well. A phone call from the airport could have led to his arrest.

There was no phone call, however, and last Tuesday he arrived back in London.

Mascarenhas writes about what he saw in East Pakistan with special authority and objectivity. As a Goan Christian by descent, he is neither a Hindu nor a Muslim. Having lived most of his life in what is now Pakistan, having held a Pakistani passport since the State was created in 1947, and having enjoyed the confidence of many of the leaders of Pakistan since that time, he wrote his report with real personal regret. "We were told by the Ministry of Information officials to show in a patriotic way the great job the army was doing," he told us .

There was no question of his reporting what he saw for his own paper. He was allowed to file a story, which was published in The Sunday Times on May 2, which reported only the events of March 25/26, when the Bengali troops mutinied and atrocities were committed against non- Bengalis.

Even references to the danger of famine were deleted by the censor. That increased his crisis of conscience. After some days' hesitation, he decided, in his own words. that "either I would write the full story of what I had seen, or I would have to stop writing: I would never again be able to write with any integrity." And so he got on a plane and came to London.

We have been able to check his story in great detail with other refugees in a position to have had a wide knowledge of events in East Bengal as a whole, and with objective diplomatic sources.

EDITORIAL: STOP THE KILLING

By devoting the whole of its centre pages to one article about East Pakistan, The Sunday Times has taken a considered and exceptional step. We have done so first because this is the fullest authoritative, firsthand account so far available of the acts and intentions of the central Pakistan Government in its eastern province.

Secondly, because the story itself is so horrifyingly revealing about what the millions of refugees are fleeing from, that it needs to be told at length. The Sunday Times has checked as far as possible the accuracy of this report. But in any event, we have the fullest confidence in the integrity of our reporter, who has himself abandoned home and career in Pakistan to bring the news to the world.

The present crisis would never have arisen had it not been for Yahya Khan's commendable wish to end the military dictatorship in Pakistan by calling, last autumn, for general elections. The outlet for Bengali nationalism which those elections provided later lit the fire which has been so brutally extinguished. But long before that the seeds of disunity and dissension were sown when, in 1947, the State of Pakistan was created in two unequal sections. From that day to this, the Bengali people of East Pakistan have justifiably, felt themselves to be the unequal partner, the poor relation in a state to whose general economy they in fact contribute a large part. Moreover, in the present welter of blood and persecution, the Bengalis themselves, as our story makes plain, must bear some responsibility for their acts of retributive violence against non-Bengalis. But when all this has been said, there is no escaping the terrible charge of deliberate, premeditated extermination levelled by the facts against the present Pakistani Government. Yahya Khan may conceivably mean what he says when he speaks of a return to civilian rule and normality, But how, after what has happened, can the Pakistani Government persuade what is left of the Bengali leadership that they are brothers and equal members of the same nation?

With the Army still operating on a directive to enforce submission to the Central Government, there is the danger that if the Western Powers to whom Pakistan is now appealing for financial aid respond positively, that aid will contribute, directly or indirectly, to the army's gruesome operations. Yet totally to withhold this and other aid would simply condemn Pakistan to economic disintegration with all the extra human suffering involved.

The most hopeful formula is for the Western countries concerned, Britain among them, to make the grant of extra aid dependent upon Yahya Khan's readiness to institute a new deal for East Pakistan and specifically to ensure that his army desists from excesses. While the United Nations and the voluntary relief organizations should stand out for control over relief operations in East Pakistan, nothing call alter the fact that Pakistan is a sovereign country which cannot be forced to do what she does not want to do. The best, indeed the only safeguard, is to direct, wherever and whenever it is possible, the spotlight of publicity upon the words and deeds of the Pakistani Government in the hope that the pressure of world opinion will in the end have some effect.

Exactly what form a new deal for East Pakistan should take is very difficult to say. Whatever it is, it is unlikely that the bulk of the refugees now in India, most of them Hindus, will ever be willing to return to East Pakistan. In the present fog of war and atrocity, one thing stands out all too clearly. It is that Yahya Khan's terrible mistake, and its terrible consequences, have created a new area of instability in Asia and the world; an area comparable, in its racial and territorial elements, with the Middle East, and likely, in the future, to cause just as much misery to its inhabitants and concern to the outside world.