Will Ethiopian rebels trade relief workers for sympathy?

The 10 British, Indian, American, Irish, and Italian relief workers who have fallen into the hands of the Tigre People's Liberation Front have little to fear from their captors. They are among the best-led and best-disciplined guerrilla forces in the third world.

The TPLF denies that it has abducted the 10 volunteers, who had been working to relieve the agonies of famine in one of Ethiopia's worst-hit drought areas. The rebel group claims that the relief workers happened to be in the small town of Korem when it was taken by their guerrilla forces.

But there is little doubt that the TPLF will use the captured volunteers to gain maximum world attention for its cause - just as it did when TPLF forces captured a British family, the Tylers, some years ago.

Much less is known about the TPLF's fight against the Ethiopian military regime than about the struggle of Eritrean rebels to the north.

The TPLF maintains close relations with the Eritrean People's Liberation Front (EPLF), but does not share its separatist claims. Instead, the TPLF is fighting for a new federal type of constitution for the country and for the establishment of a democratic political system.

Although the TPLF was created by, and is led by, young Marxists, its leaders are bitterly opposed to the Marxism of the present Ethiopian leadership under Col. Mengistu Haile-Mariam. The group counts the Soviet Union and Cuba among its enemies because of their support for Mengistu's regime.

The TPLF's politburo and central committee are headed by Aregawi Berha. He was a third-year undergraduate at the University of Addis Ababa when, with a group of other young Marxist intellectuals, he set up the TPLF. Much of its initial support came from the young intelligentsia of the major towns in Tigre - like Adwa, scene of the Italian defeat, and Aksum - as well as the town of Gondar in Gondar Province, the ancient seat of the kings of Abyssinia.

These young intellectuals were preceded in the fighting in Tigre by the conservative forces of the Eritrean Liberation Front, which was led by Ras Mengesha Syyoum, the previous governor-general of the province and a son-in-law of Emperor Haile Selassie. Although the Ras - who is in the natural line of succession of the kings of Gondar - enjoyed a reputation as a liberal governor, he failed to rally mass support among peasants.

The TPLF, on the other hand, has built up its fighting strength at a remarkable rate, especially over the last three years. It now claims to control more than 85 percent of Tigre, although it holds no major towns.

The group says it has established an extensive network of military, political , and social organizations throughout Tigre - a claim that appears to be borne out by a British academic, Don Bennett, who recently returned from a three-month visit to Ethiopia. Mr. Bennett covered about 1,200 miles there, traveling as far east as the Oanakil lowlands.

He says he met no Ethiopian troops on his trip. And he says he was able to investigate the TPLF's social and educational programs and its efforts to assist the victims of drought.

The TPLF sponsors the Relief Society of Tigre (REST), which has an office in Walthamstow, London.

After the Eritreans, who have been fighting for independence for 21 years, the Tigreans offer the biggest security challenge to Mengistu's regime. Last February, Ethiopia's Army threw an estimated 50,000 to 65,000 men against the TPLF in an effort to sweep them out of the Tigre countryside.

But the campaign in Tigre has been no more successful than ''operation red star'' in Eritrea, where more than 120,000 troops have been sent against the EPLF.