Bold daylight slayings and nighttime warfare between civilians supporting Ethiopia's Marxist military regime and those bitterly opposed to it has turned this East African capital into a city of terror.

Every day some top government official, student, labor union leader or pre-military figure is gunned down in the streets by professional assassins belonging either to the pro-government Marxist All-Ethiopian Socialist Movement or the extreme leftist Ethiopian People's Revolutionary Party, which opposes military rule and demands the immediate establishment of a "people's government."

On Saturday, tourists and Western residents were eating peacefully at the poolside restaurant of the Hilton hotel when they heard half a dozen shots ring out in the street below. Rushing across the lawn, they saw two assassins speed away in a taxi and the police arrive too late to catch them.

The assassins, presumed to be Revolutionary party members, had just gunned down two officials of a neighborhood association, known here as kebeles, killing one and seriously wounding another.

The night before, nine persons, including five students, a carpenter and a house servant, were slain en masse in a student living quarters near teh main Addis Ababa University campus. Another student was gunned down at the campus gates.It is still not clear which faction was responsible for these slayings.

A few days before that, assassins dressed in police uniforms, believed to have been Revolutionary Party supporters, stormed into the headquarters of the Ethiopian Labor Confederation and shot and killed its chairman, Tewdores Bekele, and seriously wounded his top assistant.

At least seven officials of the neighborhood associations, and probably many more, have also been assassinated by the Revolutionary Party in the past three weeks. Just how many students have been slain in the urban guerrilla struggle going on here is not known, but estimates range as high as several hunderd.

Whatever the number, such slayings are a totally new phenomemon in the three-year history of Ethiopia's increasingly bloody socialist revolution.

Most of the killings are taking place in Addis Ababa, but some have also occurred in the past few weeks in Gondar in northwestern Ethiopia, where a top local official was just assassinated, and also in Asmara, the Eritrean provincial capital, where a high-ranking government appointee was gunned down Sunday.

The slayings have unnerved the more than 1 million Ethiopians living in the capital, where the struggle between those for and against Ethiopia's revolution, and the military government, seems to have reached a fever pitch in the past month.

Touching off the crisis was the "counterrevolutionary coup attempt" of Feb. 3 that resulted in the death of seven top officers of the ruling Military Council and the emergence of Lt. Col. Mengistu Haile Mariam as Ethiopia's military strongman.

The killings and resulting tension have virtually halted once again all education in the high schools and university, where students have been on strike for almost six weeks now, and have begun to affect the functioning of some ministries as well. The univeristy had just reopened in January after being closed down almost three years because of the revolution.

Ethiopians have become extremely suspicious of one another and no longer know who is friend or foe. The few scores of students who have braved the Revolutionary party's boycott of classes live in fear and jump whenever a classroom door is suddenly opened. Some of them have been slain as a warming to the others.

There are no clear saints or villains in the current crisis, and both the Socialist Movement and the Revolutionary Party appear to have organized what in effect are "assassin squads" to wipe out each other's leaders.

The Revolutionary Party claims to have about 700 urban guerrillas now operating, mostly in Addis Ababa, and has plans to increase the number to about a thousand. This, at least, is what one party leader is reported here to have told the Albanian news agency in a recent interview.

Wratever the exact number of Revolutionary Party urban commandos, there are clearly enough to sow terror among government officials, Mengistu has promised to fight terror with terror of the government's own making, and has also decided to arm 15 members of each of the 290 capital's kebeles (neighborhoods to combat the party at that level - a decision that is likely to result in more nighttime shootouts and daytime exchanges of gunfire.

The government's "assassins" are believed to be under the direction of the Socialist Movement, whose leaders run the military's Provisional Office for Mass Organization, a kind of political bureau for the Marxist party being organized here.

The top leaders of the Revolutionary Party and the Socialist Movement are well known to one another, since many of them went to the same universities in the United States or Europe or even once worked together here before taking different sides over minute ideological differences in interpretation of Marxism and revolutionary strategies.

The quarrel among "enemy brothers" seem to boil down to the one key issue of whether a military government can be really "revolutionary," with the Revolutionary Party asserting that the present Ethiopian government is "fascist" and the Socialist Movement replying that a temporary civilian military alliance of all true "progressives" is necessary.

The debate has become so bitter that each side seems to feel that it can be resolved only by terrorizing the other side into submission. The issue of whether the military should fight it out or to attempt negotiations with the Revolutionary Party was apparently the pretext for the bloody confrontation Feb. 3 among the council's top officers.

The former chairman, Brig. Gen. Teferi Bante, and six other slain officers were reported to have favored opening negotiations with the Revolutionary Party while Mengistu and his supporters rejected this approach and demanded that "revolutionary measures" be taken against the revolution's rightist and leftist opponents alike.

As many as 1,500 Revolutionary Party students have been taken into custody since the Feb. 3 confrontation between Mengistu and his rivals. Their fate remains uncertain, although last Wednesday the colonel offered to release them if they would agree to return to school. But he was greeted with jeers.

Whether his tactic of counterterror will succeed also remains to be seen, but right now the decision by both sides to fight it out in the streets of the capital with squads of assassins is paralyzing life here for everybody.