Prospects that India and Pakistan will hold talks any time soon to resolve their simmering differences diminished further today as Pakistani Prime Minister Nawaz Sharif described India's downing of a Pakistani military plane Tuesday as a "barbaric act" that will "complicate the peace process."

Speaking at the memorial service here for the 16 Pakistanis who were killed when the naval reconnaissance plane was shot down, Sharif described the incident as "military aggression" and declared that Pakistan "will do everything to safeguard our sovereignty and national interests."

"This is a very serious violation of all principles, all international laws and agreements," he said.

Tuesday's incident near the southernmost reaches of the Indo-Pakistani border, and an encounter Wednesday in which Pakistan fired a surface-to-air missile toward Indian aircraft flying near the wreckage of the downed plane, have revived tensions between the two regional rivals just weeks after a prolonged border clash ended in the Himalayan region of Kashmir.

In New Delhi, the Indian capital, Foreign Office spokesman Raminder Jassal told reporters that India wanted peace talks with Pakistan but that the alleged incursion by the Pakistani plane was "not conducive to the normalization of relations."

Indian officials said the downed plane had violated a 1991 agreement that required both countries' combat aircraft to stay 10 kilometers (6.2 miles) away from the border, the Associated Press reported. "The Pakistani plane crossed that 10-kilometer limit and intruded another 10 kilometers into our side," Jassal said.

India's national security adviser told the Reuters news agency today that the plane was the latest in a stream of aircraft sent to spy on Indian air defenses. "They want to know what our air defenses are, and they have been doing it since the month of May," Brajesh Mishra said.

Pakistan says its plane was on a training mission and was hit more than a mile inside its territory. Regardless, said a senior Pakistani Defense Ministry official in a telephone interview from Islamabad, the two countries' "no-fly" zone agreement "does not exist after the downing of an unarmed Pakistani navy plane by the Indian air force."

There were no encounters reported along the border today. But senior Pakistani military sources said that troops, missile batteries, antiaircraft guns and long-range artillery have been moved to the border, which was largely unmanned before Tuesday's incident. Foreign Minister Sartaj Aziz told the Associated Press that the air force had increased border patrols by F-16 fighters, and senior official sources said the Pakistani cabinet's defense committee had approved "shoot on sight" orders for any intruding aircraft.

During prayers for the dead naval aviators, Sharif looked moved as he and other top military officials embraced sobbing friends and relatives of the casualties. Their 16 caskets, wrapped in green Pakistani flags, had been brought to a naval base here before being flown to their hometowns on special air force flights.

"Indians must not go unpunished," shouted one of the crewmen's grieving relatives as Sharif moved to console him. "We must pay them in kind," said another. Sharif nodded wordlessly.