Two policemen, a soldier stationed there and two civilians passing by the area were slightly injured, police said.
The assailants, believed to be riding on a motorbike or in a car, fled the scene.
At least one vehicle was damaged and police were said to be in pursuit of the attackers.
The Beirut area has seen three big explosions in the last week, killing a woman and injuring nearly 30 people.
The violence came as Lebanese troops were fighting Islamic fighters at the Palestinian refugee camp of Nahr el-Bared in northern Lebanon.
Scores of people have been killed in the week-old fighting.