Sri Lanka's minister for national security, Lalith Athulathmudali, said today he plans to relax curfew restrictions in the northern province of Jaffna, where Tamil separatist guerrillas are battling government troops.

Following an hour-long meeting here with Indian Prime Minister Rajiv Gandhi, Athulathmudali said he hopes to ease the restriction of movement in a "prohibited zone," 100 yards inland from the shoreline around the northern province into which no Tamils are allowed to enter. Creation of the zone has put tens of thousands of fishermen out of work, resulting in food shortages in the Jaffna peninsula at the northern tip of the island nation.

"I'm very conscious of the fact that I've had to put the civilian population at a great inconvenience. I'm trying to work out means to put the fishermen back to sea," Athulathmudali said in an interview after his meeting with the Indian prime minister.

Gandhi is understood to have expressed India's concern about continued violence by Sri Lankan Army troops against Tamils in the northern and eastern provinces, where the separatist insurgency has worsened in the last year, resulting in at least 500 deaths.

Athulathmudali, who also met with Indian envoy R. Parthasarathy, chairman of the Foreign Ministry's policy planning committee and the chief negotiator on the Sri Lanka problem, refused to discuss details of his meeting with Gandhi, saying he had not yet reported to President Junius R. Jayewardene.

He said, however, he believed that a Sri Lankan Navy blockade of the narrow Palk Strait separating Jaffna from the southern Indian state of Tamil Nadu had been partially effective. He said the insurgent groups, which previously had been able to send troops and supplies freely across the strait, were now unable to sustain a prolonged offensive. The supply line has long been a point of contention between India and Sri Lanka, with Sri Lanka also charging that Tamil guerrillas are being trained at bases in Tamil Nadu.

Athulathmudali said Sri Lanka had provided India previously with a list of about 10 alleged guerrilla training bases in southern India, but he would not say whether he had discussed that issue with Gandhi.

An Indian Foreign Ministry spokesman refused to discuss the Indian interpretation of the meeting between Gandhi and Athulathmudali, which was not attended by any aides, other than to say there had been a "useful exchange of views on the Sri Lanka situation."

When asked about reports that Athulathmudali had secured a pledge from U.S. officials during his visit last month to Washington that the United States would apply economic pressure on India to curtail guerrilla operations originating in southern India, Foreign Ministry spokesman Salman Haider replied, "We have seen these reports, but we are unable at this stage to make any substantive comment."

Athulathmudali's visits to Washington and London aroused considerable interest in New Delhi because officials viewed them as shopping trips for sophisticated arms to use against the guerrillas. India has urged Sri Lanka to seek a political rather than military solution to the conflict.

The Associated Press reported that airport officials in the southern city of Trivandrum detained briefly a Zairian DC8 cargo plane whose crew told reporters it was carrying ammunition from Jordan to Sri Lanka for that nation's Army.