Warring factions in the Chadian capital of Ndjamena reportedly agreed to a 48-hour cease-fire yesterday to allow civilians to escape intense fighting that is believed to have caused as many as 1,000 deaths in a week.

A relatively quiet night in the embattled capital was broken at dawn yesterday by mortar fire, followed by heavy exchanges of artillery, machine guns and small arms, according to news agency reports.

The cease-fire was proposed by the International Committee of the Red Cross, which cited "catastrophic" health conditions in the capital, where factions supporting President Goukouni Oueddei and Defense Minister Hissene Habre have battled since Friday.

Authorities in neighboring Cameroon said at least 30,000 refugees have crossed the Chari River into that country. Many are encamped in the border trading town of Kousseri.

In a dispatch from Ndjamena, Agence France-Presse reported that a source close to Goukouni said the cease-fire would go into effect at 4 a.m. Saturday. The two sides have agreed to several temporary truces this week -- including earlier yesterday -- but they were violated virtually as soon as they took effect.

There was no guarantee that the latest cease-fire would be respected either.

A former French colony in northcentral Africa, Chad has been in a state of virtual civil war since it became independent in 1960. About 1,100 French troops remain to help keep the peace and France sends approximately $50 million in aid a year.

For most of the 20 years since independence, Chad was ruled by Christians and adherents of tribal religions in the south. A shaky coalition led by Moslems but including all Chad's 11 armed factions took control last year.

This week's fighting in the capital apparently was triggered March 14 when a clash broke out between forces loyal to Habre and Interior Minister Abba Seid at the headquarters of the coalition's security forces in the town of Bokoro, 185 miles east of the capital, according to diplomatic sources here.

U.S. officials said it was unclear what triggered the original outbreak, and suggested that the latest fighting was more likely the result of personality conflicts among the leaders of Chads many factions than ideological strife.

In addition to the Red Cross, French, Egyptian and Saudi diplomats were pressing efforts to reach a settlement and Sudanese President Jaafar Nimeri yesterday called for a special Organization of African Unity committee to seek an end to the fighting, according to a newspaper in Sudan.

U.S. officials noted that the peace-keeping efforts face increased obstacles, however, as more groups appear bent on entering the fray. They expressed particular concern over reports that forces backing Vice President Col. Wadal Abelkader Kamogue, a southern Christian, have moved toward the capital and were attacking Habre's troops.

Habre, who has accused Koukouni and his allies of being under Libya's control, appears to be the odd man out in the latest fighting, with his forces being pinched by those of Koukouni, Seid and Kamogue.

The French troops stationed in Chad have studiously avoided intervening in the conflict, and French President Valery Giscard d'Estaing yesterday issued a statement saying France would limit its assistance to giving humanitarian and medical aid and contributing to efforts to work out an effective cease-fire, Reuter reported from Paris.

U.S. officials and representatives of Chad's embassy here stressed yesterday that it is difficult to sort out the extent of casualties and damage because of the sparse communications with Ndjamena. All. U.S. Embassy personnel were evacuated by Monday, and the Embassy of Chad has had no direct contact with the capital since Saturday.

Diplomatic sources said reports that at least 1,000 persons have been killed are plausible and pointed out that the capital of the poverty-stricken nation has been without water and electricty. Food is also in short supply, they said.