Gen. Joseph Lagu, leader of Africa's longest secessionist struggle, says today that a five-year experiment in regional autonomy for his people here in the southern Sudan has been a total success and that the wounds of the 17-year-long civil war are now healed.

"There is stability and there is peace," the general said in an interview on the veranda of his residence inside the compound of the First Division, which he still commands. Relations between the Sudan's Arab north and African south are "excellent," he said.

The former Anyanya guerrilla commander dismissed the attempt by a company of soldiers to seize Juba airport a month ago as one of a number of "minor disturbances" that have periodically marred the initial five-year trial period of the peace agreement signed in Addis Ababa, the Ethiopian capital, in 1972.

The accord is widely regarded as President Jaafar Nimeri's most important political achievement to date and has also been hailed across the continent as an African victory over the separatist tendencies threatening the national unity of many newly independent African countries.

Ironically, Sudan's Unity Day Celebrations this year were held only two months after Nimeri decided to change his own policy toward another secessionist struggle under way next door in Eritrea, the northernmost Ethiopian province, and to support the Eritreans in their bid for independence. The change came after Nimeri became convinced, rightly or wrongly, that Ethiopia's radical military rulers were out to topple him from power.

The long and bloody civil war here, in which several hundred thousand people are estimated to have died, pitted the south, inhabitated by black Africans, some of them Christians, against the Arab and Moslem-dominated north. Lagu, 46, himself a southener from the Latuka tribe, defected from the northern army in 1963, joined the Anyanya guerrillas, and seven years later emerged as the military and political leader of the Southern Sudan Liberation Movement. The term Anyanya is a Latuka word meaning "snake venom" or "incurable poison."

With Israeli help, Lagu turned the ragtag Anyanya guerrillas into a semi-professional fighting force of 18,000 soldiers that successfully held off all efforts by the central government's far stronger army to crush the movement.

The outcome of the struggle was a special status for the three southern provinces of the Sudan, giving the black southerners regional autonomy with a separate Parliament and a High Executive Council.

Gen. Lagu has spent the past five years overseeing the delicate task of integrating the Anyanya guerrillas into the national army's First Division, based in the south. He says the Anyanya now make up more than half the division's total force of 12,000, although the officer corps is apparently still dominated by northerners.

Assuring peace and stability in the southern Sudan, of which Lagu so proudly brags today, has not been without its trials for the architects and supporters of the Addis Ababa accord. The "minor disturbances" that have periodically punctured the peace have involved small groups of disaffected Anyanya guerrillas and diehard southern separatist politicians who oppose the peace agreement and have gone into opposition.

More recently, northerners opposed to President Nimeri have also apparently joined in trying to upset the peace agreement as a means of discrediting and undermining his rule. Nimeri, and local officials here as well, insist that Libya and Ethiopia are now involved in these efforts.

Despite these continuing threats to the peace agreement, it appears to have held up relatively well so far and to be taking root in a slowly expanding regional administration that has given the African southerners at least a measure of home rule, but above all peace and their first chance for economic progress.

"We can now go to bed at night and not have to worry about being killed in our beds before dawn the next day," said one southerner, who nonetheless expressed mixed feelings about the south's fate under the Addis Ababa accord.

A handful of disgruntled southern politicians, some of them members of the 60-member People's Regional Assembly, continue however, to stir up resentment against the peace agreement.

These dissidents include Philip Pedak Lieth, an assembly member who fled to Ethiopia last year; Benjamin Bol Akok, the body's deputy speaker, and Joseph Oduhu, also a regional deputy. The latter two were arrested last March for allegedly plotting against the Addis Ababa accord and are being held prisoner in the Juba jail.

Pedak has tried to revive the old Anyanya movement, making use primarily of refugees who enter Ethiopia to escape the troubles that periodically have erupted in southern Sudan since 1972. These troubles have mostly involved mutinies by Anyanya troops in half a dozen locations throughout the south, all of them quickly contained. The refugees now number only a few thousand, but at one point in 1975 there were more than 10,000 who fled into southwest Ethiopia after a clash between Anyanya and northern soldiers.

Pedak contends that the south has gotten a raw deal under the Addis Ababa agreement."We in the south want nothing less than total independence," he declared last year. "We have failed to make the Arab north live with us side by side and although there is an assembly to legislate and a High Executive Council to run administrative affairs in the south, both organs have no power. They are being dictated and directed from Khartoum by the Sudanese Socialist Union, whose leaders are always from the northern Arabs of the Sudan."

The economy of the south is still woefully backward. Only 18 per cent of school-age children are being educated; schools are constantly being shut down because teachers are not paid for months at a time; the road network remains one of the world's great obstacle courses; and transportation up and down the Nile River between Kosti and Juba has actually gotten worse since 1972.

The south is still so underdeveloped that it has been unable to absorb even the assistance available. Every development project so far started -- a dozen or so agricultural plans and factories -- has encountered delays of months and even years because of the multitude of obstacles, ranging from shortages of fuel and manpower to government bungling at both the regional and national level.

Altogether, the south's economic straits seem to stem as much from this bottleneck as from southern charges of funds being withheld by the north. Still, the southerner's suspicion of the Arab north, particularly among the English speaking intellectuals, remains a leitmotif of politics here.