NEW DELHI, Nov. 7—Unimpeachable Indian sources said today, despite official denials, that Indian troops had crossed into East Pakistan to silence Pakistani guns that had been shelling Indian territory.

This was the first reliable assertion that Indian soldiers had operated inside East Pakistan since the India‐Pakistani border crisis began intensifying about a month ago.

The Indian military sources said that Indian troops had crossed over on Oct. 31 and Nov. 1, in retaliation against what Indian officials had described as 11 continuous days of Pakistani shelling of Kamalpur, a border town in the northern part of Tripura Territory, northeastern India.

Indian officials reported at least 20 civilian casualties and heavy property damage in the town, which has a population of about 4,000.

On Nov. 1, the day the two‐day clash reportedly ended, a Defense Ministry spokesman, discussing the incident at one of the Government's periodic briefings on the border situation, said that Indian troops had been “forced” to take “counteraction” against Pakistan for the first time in the current border crisis.

The spokesman said the “counteraction” had stopped the shelling, mostly from mortars, and that “We hope there will be no further trouble” in that area. But he sidestepped all questions on the details and nature of the fighting and on whether Indian troops had crossed into Pakistani territory.

Two days later, at a similar briefing, the Government spokesman issued a “clarification” to “correct” local newspaper reports, growing out of the previous briefing, that had suggested that Indian troops might have crossed the border. He said the soldiers had definitely not crossed the frontier and had “strict orders” not to do so.

The high Indian military sources that now have confirmed that Indian forces did cross the border declined to discuss the number of troops involved, the kinds of weapons they used or the number of casualties of either side. Other sources have indicated that at least 100 Indian soldiers had crossed over.

It is not known how far into East Pakistan the soldiers went. But since most of the Pakistani guns were reported to be mortars, with ranges of only a few miles, and not heavy artillery, the penetration would not necessarily have been very deep.

For the last two weeks, Pakistan and India have been exchanging charges of troop intrusions, primarily along the border with East Pakistan, which is separated from West Pakistan by more than 1,000 miles of Indian territory. They have also accused each other of shellings, air‐space intrusions and violations of the cease‐fire line in Kashmir, where they fought a brief War only six years ago.

But neither side has publicly mentioned a Kamalpur border‐crossing and clash, which would constitute the most serious incident since both countries moved the bulk of their forces to battle stations along the borders a few weeks ago. Some diplomatic observers have speculated that the two countries are trying to avoid public discussion of really serious incidents out of fear of impelling their civilian populations into a momentum toward war.

The Indian‐Pakistani border confrontation is an outgrowth of the seven‐month military crackdown by Pakistan on the Bengali separatist movement of East Pakistan, which resulted in a flight of refugees that India now reports has totaled more than 9.5 million people. This has imposed a severe burden on the Indian economy.

India has been providing the Bengali insurgents, known as the Mukti Bahini (Liberation Forces), with border sanctuary and military assistance. It is not known whether Mukti Bahini activities had anything to do with the shelling of Kamalpur, but the insurgents are believed to have base camps in that area.