Delhi, Nov 1
An Indian Defence Ministry spokesman said today that Indian guns had opened fire on a Pakistan aircraft which flew over Srinagar, the provincial capital of Kashmir, at noon today. The spokesman said that the aircraft was detected by radar as it approached the capital at high altitude above the clouds.

The incident was described as the most serious development since the growth of tension between the two countries.

The spokesman also disclosed that Indian troops had effectively silenced Pakistan units which were said to have continually shelled the small Indian town of Kamalpur. three miles from the Indo-Pakistan border in the eastern state of Tripura.

Government officials refused to give details of the clash, but the Defence Ministry spokesman admitted that both sides had suffered casualties. He added that India had decided upon retaliatory action after Pakistan shells had destroyed several buildings in the small border town. Mortars, artillery and machineguns were used during the 24-hour skirmish.

“According to our latest reports”, the spokesman said, “the Pakistan guns have been put out of action and they are silent.”

It is understood that Indian troops also made a quick foray into East Bengal to push back Pakistan units which had presumably been firing on guerrilla bases near the border and near Kamalpur.

The Ministry of Defence said that today's air violation was the second of its kind within two days and the Government had lodged a strong protest with Pakistan.

Mr Jagjivan Ram, the Minister of Defence, told journalists in Nemuch, Madhya Pradesh, today that India would never start a war, but if a conflict did break out the fighting would take place this time on Pakistan soil, not Indian soil.

The Indian Government claimed today that Pakistan was attempting to increase tension near the sensitive cease-fire line in Kashmir. A spokesman said that Pakistanis had violated the 1965 cease-fire agreement on 21 occasions since October 27 and 159 times in the month of October.

Asked to describe the nature of these violations, the spokesman said that Pakistan troops had built bunkers and trenches near the border. The agreement had stipulated that both sides should not construct military installations within a specified distance of the frontier.