Sri Lankan security forces have detained at least 600 Tamils for questioning as suspected guerrillas in the heavily contested Trincomalee area in the eastern part of the country, the area security commander confirmed today.

Many of those arrested were being shipped to a detention camp south of the capital, Colombo, for questioning, according to Col. Lakshman Wijayaratne, who said in a telephone interview that the questioning process may be lengthy.

It is one of the largest detention campaigns launched against Tamil guerrillas, whom the government labels as terrorists because of their many bombings and ambushes directed against civilian targets.

The arrests, which began with a massive security sweep of the crowded port area of Trincomalee on Tuesday, clearly represent a fight-and-talk strategy on the part of the government of President J.R. Jayawardene.

On Wednesday, Jayawardene outlined a new peace program offering considerable provincial autonomy to meet some of the demands of this country's 3 million Tamils, whose more militant elements have been fighting a bloody guerrilla war against the Sinhalese majority.

At a rare news conference yesterday, however, Jayawardene said that the government would not meet guerrilla demands for a cease-fire in order to draw them into peace talks, and that it plans to continue buying new arms to fight the guerrilla war.

A leading Cabinet minister confirmed today that, at least in the short run, the government has no intention of pulling its troops back into the barracks while Tamil moderates and militants decide how to respond to the new peace proposals. Jayawardene has said he intends to push his proposals through Parliament, whatever their answer.

Tamil political leaders ended two days of talks in New Delhi with Indian officials who have been attempting to bridge differences between them and the Sri Lankan government.

Sri Lankan Tamils share a language, culture and the Hindu religion with the Tamils of southern India, where Tamil political leaders are in exile, while the Sinhalese-speaking Sri Lankans are mostly Buddhists.

Diplomats familiar with India's posture toward the current talks today called the Sri Lankan security sweeps "not helpful."

Tamil guerrillas are in virtual control of the northern part of the country, but the Eastern Province, which is evenly split along ethnic lines, is seeing increasingly bitter fighting.

In addition to the large number of detentions, security officials in Colombo said today that 10 guerrillas had been killed and a large amount of ammunition found after a heavy firefight near Batticaloa, south of Trincomalee.

While most of the detentions were reported in Trincomalee, the site of the country's major naval base, Col. Wijayaratne said 70 others were detained after two guerrillas were killed in a gun battle in nearby Nilavali, an area highly sympathetic to the Tamil guerrilla cause.

Reports that the number of detentions is actually far higher than the 600 claimed by security officials could not be confirmed.