ABOARD AN INDIAN AIR FORCE TRANSPORT PLANE, JUNE 4 -- Indian Air Force planes, escorted by fighter jets, swooped over Sri Lanka today and dropped nearly 25 tons of relief supplies to ethnic Tamil residents, an act that apparently led Sri Lanka to suspend its military offensive against Tamil rebels in the region.

India dropped the supplies near the northern city of Jaffna, in defiance of Sri Lanka's refusal to accept a unilateral Indian aid mission to the Tamils, many of whom are fighting a four-year-old guerrilla war for regional autonomy. Sri Lanka protested the air drop as "a naked violation of our sovereignty . . . and territorial integrity."

The Indian airlift appeared to send a stiff warning to the Sri Lankan government against its 11-day-old offensive aimed at crushing the military stronghold of Tamil guerrillas in Jaffna.

{Officials in the Sri Lankan capital, Colombo, said the Army would cancel a planned second offensive in the Jaffna region, The Associated Press reported. A military official, speaking privately, said the suspension of the offensive was a political decision, designed to calm Indian anger about the offensive.}

"We have no military or other means of preventing this outrage," a Sri Lankan government statement said. "We will take this up in an appropriate forum."

In what the Indian government code-named "Operation Eagle," five Indian Air Force Antonov AN32 transport planes took off from Bangalore in southern India and were joined by French-built Mirage 2000 jet fighters as they flew through sunny skies across the 30-mile-wide Palk Strait to Sri Lanka.

As the formation entered Sri Lankan airspace, Indian officers said, they radioed to air control authorities, informing them that they meant to drop the supplies into Jaffna. There was, they said later, no response from the Sri Lankans.

Over Jaffna, which has been the center of bitter fighting for the past week, the transports descended to 1,200 feet while the fighter escort wheeled above. Loading-bay doors opened and supplies of rice, milk powder, vegetables and kerosene fell to earth under billowing parachutes.

India has charged that Sri Lanka has killed hundreds of civilians in the Jaffna region by "carpet bombing" raids. From the Indian planes, the 35 journalists invited to witness the mission could see no evidence of aerial bombing, although a few clumps of trees near the drop point had been burned.

The area appeared eerily lifeless; no smoke rose from the chimneys and no vehicles or people moved in the streets. But most of the rooftops looked intact.

There was no evidence of any Sri Lankan effort to defend against the Indian flight. Sri Lanka's Air Force possesses no fighter planes, and has used converted propeller-driven trainer aircraft in its battle against the Tamils. The commander of one of the Indian transport planes said afterward "our brief was to carry on the mission regardless" of Sri Lanka's refusal.

The airlift culminated a week of confrontation between Sri Lanka and India over Sri Lanka's operation to regain control of the island's northernmost Jaffna Peninsula.

The Indian government, under heavy pressure from its own 50 million Tamil citizens in southern India, first sent a flotilla of ships to deliver supplies to Tamils in Jaffna, who India has said are starving because of a government blockade of the area. Sri Lanka, which says it is delivering sufficient relief supplies to civilians there, turned back the Indian boats yesterday, saying details of any Indian mission would have to be negotiated between the two governments.

{Thursday morning, Sri Lankan President Junius Jayewardene sent a message to Indian Prime Minister Rajiv Gandhi asking that a negotiator be designated to discuss how supplies might be delivered, according to Naren Chitty, the Sri Lankan Embassy press counsellor in Washington. Citing a government statement issued in Colombo, Chitty said, "The Indians called in our {ambassador in New Delhi} at 2 p.m. They told him that an airlift would be launched about 35 minutes after the end of that meeting." There was no formal response to the Sri Lankan offer of negotiations, Chitty said.}