BEIRUT, Lebanon (AP) _ A week ago Suha Chanine was a beautiful university student who had been chosen Miss Lebanon. Now she is a casualty of this ravaged nation's long civil war, her body broken and her face torn by shrapnel.

She lay in a hospital Thursday in critical contition, comatose. Surgeons have removed her spleen and taken shell fragments from her right lung.

Miss Chanine, 21, and Zeina Tadmurri, her roommate at the American University of Beirut, were wounded by a stray 81mm mortar shell that exploded on the tree-lined campus Sunday during the heaviest fighting between Christian and Moslem militias in two months.

They had left their dormitory to get a soft drink.

Two other students were wounded by the stray round. A medical student and a doctor were killed.

The university is in Moslem west Beirut, and police said the shell came from a mortar on the Christian side of the line that divides the city according to the predominant religions of its neighborhoods.

Officials at the university hospital said Thursday that Miss Chanine, a sophomore studying political science and public administration, was in the intensive care unit.

She was chosen Miss Lebanon a few months ago for the Miss World and Miss Universe pageants, but even such a seemingly innocent distinction could not escape the sectarian enmity that has bathed Lebanon in blood for a decade.

She is a Moslem and the Tourism Ministry disqualified her, arguing that the contest was unfair because Christians were not equally represented.

''She walked out with her roommate from the campus dormitory to get a drink of juice when the shell hit,'' said her father, Mohammed Chanine, a 55-year- old auto salesman.

The family lives in the Mazraa neighborhood near the no-man's-land of waste, gutted buildings and rubble that divides the city and is inappropriately called the Green Line. Mazraa's location makes it a regular target for random shelling by Christian forces.

''I got her to stay in a dormitory on campus so she wouldn't have to go on the streets and to keep her away from the shelling near our home,'' Miss Chanine's father said.

''But a shell got her on campus anyway. The shelling was criminal. These are students who are guilty of nothing,'' he said. ''She usually comes home on weekends. But this time she stayed on campus to study.''

Statistically, Miss Chanine was just unlucky. Police estimated that more than 3,500 artillery, mortar and rocket rounds were fired on residential neighborhoods in east and west Beirut Sunday and Monday.

Few of them claimed victims because the Lebanese have learned to duck and hide. Police said 14 people were killed and 76 were wounded in the two days.

Miss Chanine, however, lies in a coma, tubes inserted in her nose. Her father, her sister Rima, 19, and relatives wait for her to regain consciousness.

She is improving slowly. ''We hope the danger is over,'' Chanine said.

Government officials estimate that at least 100,000 people have been killed since the civil war began 10 years ago. Tens of thousands have been maimed and wounded.