LUANDA, Angola (AP) _ Government and rebel forces reportedly clashed outside Luanda today, but the capital was generally quiet under a U.N.-sponsored truce after days of bloodshed that killed up to 1,000 people.

Among those reportedly killed were the UNITA rebels' second-in-command and a nephew of rebel leader Jonas Savimbi.

People ventured out in Luanda for the first time since battles erupted in the city Saturday. But tensions remained high and many people feared the country was headed for renewed civil war after a year under a peace accord.

The civil war, which broke out in 1975 as Angola was becoming independent from Portugal, became one of the Cold War's major proxy fights. UNITA - the National Union for the Total Independence of Angola - was backed by the United States, while the ruling MPLA - the Popular Movement for the Liberation of Angola - was supported by Cuban troops and Soviet aid.

Witnesses said today a convoy of military vehicles moved out of Luanda toward northeastern Bengo province, where UNITA rebels were reported last week to have massed 7,000 soldiers.

Some fighting was reported in the towns of Viana and Caxito just outside the capital and occasional shooting was heard in the city's sprawling shanty towns.

In a statement, the government army said 14 top UNITA officers were captured during fighting in the capital, in which bands of armed civilians joined government police units in flushing out rebels.

State radio said UNITA leaders might be swapped for three senior government officials seized by rebels last week in the central city of Huambo, where Savimbi has his base.

The U.N.-brokered cease-fire went into effect early Monday and fighting gradually died down in Luanda.

The clashes between UNITA and the ruling MPLA erupted in the provinces on Thursday and spread to Luanda on Saturday. They threatened to plunge the southern African nation back into the civil war that ravaged the country for 16 years and killed 350,000 people. The fighting ruptured a 1991 peace accord that paved the way for elections in September.

UNITA ran second to the MPLA in the parliamentary elections, and Savimbi trailed incumbent Eduardo Dos Santos in the presidential race. Although U.N. observers deemed the balloting generally free and fair, Savimbi charged the vote was rigged and threatened renewed war.

UNITA has said it did not begin the fighting in Luanda. Jardo Muekalia, a UNITA spokesman in Washington, said Luanda police armed civilians to help conduct ''a house-to-house hunt for UNITA sympathizers and supporters.''

Many of the civilian fighters were thought to be veterans of the government army who were demobilized under the peace accord. But others were reported to be teen-agers.

Amnesty International said it had received reports of several summary executions in Luanda and the provinces but the London-based human rights group gave no details.

Armed bands reportedly looted property Monday night, but witnesses said police restored order after an overnight curfew was imposed.

UNITA reportedly holds large sections of the countryside and has concentrated forces in the central highland region around Huambo, Angola's second largest city, 310 miles southeast of the capital.

Police said UNITA's No. 2 official, Jeremias Chitunda, and Savimbi's nephew Elias Salupeto Pena were shot and killed while trying to flee Luanda. Another Savimbi nephew, Arlindo Chenda Pena, a top rebel military officer, was wounded while trying to escape, officials said.

Carlos Fontoura, a rebel spokesman in Lisbon, denied reports Savimbi had fled to Morocco or South Africa. He said the rebel chief remained in Huambo.