NEW DELHI, Dec. 2—Indian Government spokesmen said tonight that the large Indian force that entered East Pakistan five days ago had advanced and cut a railroad line that supplies the northwest corner of that country.

An official statement said that there was “a lull in the fighting” today near the border town of Hilli, about 185 miles north of Calcutta, after Pakistani troops withdrew.

The Indian intention seemed to be to remain within East Pakistan for the time being.

One spokesman said that the immediate objective of the Indian military action was to silence Pakistani artillery, which has shelled Indian border villages and positions. India's overall objective, he said, was to “make it possible for 10 million refugees to go back.”

Incursions Called Defensive

The refugees have fled to India since Pakistani forces—largely from West Pakistan—began to use force last March to crush an autonomy movement in the east.

The Indian force crossed the border near Hilli on Saturday in the latest of several of what India calls “defensive action” border incursions.

Indian officials again declined on security grounds to give the size of the Indian force involved at Hilli. Informed sources, however, said that it was a reinforced infantry brigade or more—more than 3,000 men and possibly more than 4,000. About 45 Soviet‐built medium tanks were also said to be involved.

The Indians said that they had been opposed by a Pakistani brigade and 14 light tanks, but that the tanks had been withdrawn after five were knocked out.

The spokesman said today that the Indians had penetrated “three, four or five miles.” On Monday they put the distance at two or three miles.

Line Reported Blocked

The Indians had reached and blocked a railroad line north and east of Hilli, the spokesmen said. The line connects the northwest part of East Pakistan to the south.

Further rail traffic in the immediate area would ,no longer be possible, one spokesman said. He added, however, that “our information” is that guerrilla activity by the East Pakistani Mukti Bahini (Liberation Forces) had already stopped the trains running from Jessore city in the south to Hilli.

[The Pakistani radio, monitored in New Delhi, tonight asserted that Pakistani troops had pushed the “intruding” Indian troops from the rail track, United Press International reported.]

Questioned about the request of President Agha Mohammad Yahya Khan of Pakistan to Secretary General U Thant that United Nations observers be stationed on the East Pakistani side of the border, spokesman said that India could not guarantee the physical safety of such observers.

At one point in a press briefing the Indian spokesman said that “we feet that an attempt is being made to rescue Yahya Khan out of, his difficulties and leave him carry on his devastation in East Bengal [East Pakistan.]”

Another spokesman said “there is no reason to believe” that the guerrillas would respect the safety of foreigners stationed near the border in East Pakistan.

He said that India would not attempt to restrain the guerrillas, adding, “We are not about to tell them what to do and what not to do.” He said he could not see why India should be bound by “cricket club rules.”