JAMMU, India -- Indian and Pakistani troops exchanged sporadic fire across the border in disputed Kashmir for the second day on Tuesday as tensions escalated despite a visit to the region by U.S. Secretary of State, Colin Powell.

A senior military official told Reuters in Jammu, winter capital of the northern state of Jammu and Kashmir, that mortar bomb and heavy machine gun fire was exchanged across the border in the morning but the intensity had later receded.

"There is intermittent firing in the Akhnoor and Mendhar sectors. It was heavy in the morning but has now receded," the official said.

The fierce gunbattle between the nuclear rivals that began on Monday had continued through the night, in the most serious shooting in nearly a year across the military Line of Control that divides Kashmir.

President, George W. Bush, called on Monday for both Islamabad and New Delhi to cool tensions.

"I think it is very important that India and Pakistan stand down during our activities in Afghanistan and, for that matter, forever," he told reporters.

The shooting comes amid increasing frustration in India about Washington adopting Islamabad as its key ally in its war against terrorism, and rising international concern that New Delhi might strike back at Pakistan for supporting militancy in Kashmir.