Four men were shot outside a Brooklyn bar early Monday, law enforcement sources said.

A loud group inside the D Avenue Lounge, at 673 Flatbush Ave., was thrown out after someone hit the bouncer in the back of the head with a bottle, police said.

Once those rowdies were tossed, they ran into another group just outside the bar and began fighting at 3:24 a.m., authorities said.

At least one person pulled a gun and four men were wounded in ensuing gunfire — a 30-year-old shot in the neck, a 24-year-old grazed in the elbow, a 34-year-old shot in the arm and another 30-year-old hit in the groin, thigh and shin, officials said.

All four victims were taken to the hospital and listed in stable condition. The bouncer, who was cut in the back of his head, declined treatment.

No one was immediately arrested and cops are still looking trying to find a motive for the battle.