Guerrillas fighting for the independence of Eritrea, Ethiopia's northernmost province, appear to be making steady military gains against increasingly war-weary troops of the Ethiopian military government, despite the rebels, preoccupation with worsening political divisions within their own ranks.

In fact, Eritrean sources here express considerable concern that the battle-scarred Red Sea province might unexpectedly gain its independence even before the intense factionalism bedeviling the 15-year-old movement can be resolved. This, they say, could open the door to an Angola-style civil war within Eritrea, involving the neighboring Arab states and possible even the big powers as well.

Fear of a "premature" independence apparently explains the surprising lack of enthusiasm manifested here now by some Eritrean Liberation Front officials for a victory that could come simply as a result of the Ethiopian army's refusal to fight on any longer.

While the eventual independence of Eritrea is far from certain still, the war is an important bellwether in Africa, for should this happen it could have wide repercussions throughout the continent. In effect, it would undo the "lesson of Biafra," the continent's first great civil war, in which federal Nigerian troops finally prevailed in 1969 over a breakaway movement in the eastern part of that country, but only after a long hard struggle.

Biafra, like the 17-year-long civil war in southern Sudan, ended in a victory for the integrity of African states such as they were handed down from the Western colonial powers. Eritrea, now Africa's eldest civil war, could set a dangerous new precedent, calling into question the whole, jigsaw-like pattern of boundaries throughtout Africa.

While there is no indication that the army has reached that point yet, there have been numerous signs recently of a serious malaise among the estimated 25.000 to 27,000government troops stationed in Eritrea.

In the past few weeks, more than 200 soldiers were reported to have either surrendered to rebel forces or sought asylum in Sudan. In addition, the Eritrean Liberation Front last month captured three army garrisons and two towns along the Sudanese border, partly, it seem, because of a collapse of morale among Ethiopian troops.

Another 214 troops also went over to a second opposition group. The Ethiopian Democratic Union, in Begemdir Province south of Eritrea.

Front sources here said the next major offensive would be against the army garrison in Naqfa, where about 200 government troops have been under siege for four months. This would leave the rebels in control of all of the province north of Keren and could further demoralize the army.

In mid-January, a delegation from the Ethiopian army's 2d Division, based in the Eritrean provincial capital of Asmara, went to Addis Ababa to discuss the battlefield situation and reportedly also to press the central government to negotiate immediately a solution to the war.

In fact, the ruling Provisional Military Council spent most of last year in an unsuccessful search for a political settlement. It has offered the Eritreans a nine-point program leading to some kind of regional autonomy, but the rebel front has been unwilling to negotiate anything less than the province's total independence.

Eritrea is vital to the central government because it contains Ethiopia's only two ports and access to the sea. About a third of all Ethiopian industry is located there. But only about 2 million of the country's 28 million to 30 million people live in the old Italian colony, which was reunited with the rest of Ethiopia in 1952.

Despite the Eritrean Liberation Front's recent successes, a spokesman here predicted no all-out offensive by the movement in the immediate future to take advantage of its sudden new military momentum.

"We must resolve our political differences first," he said in an interview. "Otherwise, it will be very serious later."

Eritrean sources here report that practically no progress has been made in the past two years in efforts to reunify the two main guerrilla faction of the Arab-backed seccessionist movement - the Eritrean Liberation Front-Revolutionary Command and the Eritrean People's Liberation Forces.

A third faction has developed under the leadership of Osman Saleh Sabe, a former top leader of the Liberation Forces.

Sabe has strong backing from Iraq and a small guerrilla force numbering between 2,000 and 3,000 men, according to these sources. the Eritrean Liberation Front has about 22,000 disparately armed fighters and the Eritrean People's Liberation Forces have 12,000.

Ideological and political differences among the various Arab states supporting the Eritrean seccessionist movement since its creation in late 1961 have complicated unity efforts.

Since September 1975 when the two main groups signed a unity agreement, the Eritreans have been debating ways to unify themselves under one military command and one political leadership. The agreement called for a joint congres of the two factions in early 1976, but it was never held because the accord was rejected by the military leaders of the People's Liberation Forces.

In fact, that faction's guerrilla leaders fighting inside Eritrea disowned Saleh Sabe and threw him out of the party in dispute over the unity agreement and his leadership.

Westerners often attribute the differences among the Eritrean factions to religious and ideological quarrels and describe the People's Liberation Forces as more Christian and Marxist and the Liberation front as predominantly Moslem and more Arab nationalist.

But Liberation Front sources here say that their movement is now 60 per cent Christian, and that the divisions stem primarily from the feuding among the leaders.

The People's Liberation Forces is holding a congress inside Eritrea to discuss, among other things, the basis for unity talks with the Liberation Front. It has refused so far to sit down at the same table with Sabe, who is holding talks here with his followers.

Whether the three factions will get together remains doubtful, and it is this prospect that deeply concerns many Eritreans here.

Meanwhile, the movement appears to be steadily gaining ground against the Etiopian army. The most recent army garrison to fall was Telatacher, about 13 miles west of Tessenay. A company-size force withdrew on Jan. 22 to the much larger garrison in Tessenay.

The guerrillas now seem to be concentrating their efforts on forcing the arm to evacuate outlying isolated garrisons like Telatacher before they attempt to lay siege to the main towns and cities where the army is still deeply entrenched.

The guerrillas now control most of the province's countryside and a growing number of small towns and villages along the Sudanese border, while the army is concentrated in half a dozen urban areas - Asmara; the two Red Sea ports, Asab and Massawa; Agordat, Keren and Tesseanntts.