Two men and two women were wounded in the shootout around 9:30 p.m. local time, the Associated Press reported, quoting New Orleans police spokesman Frank B. Robertson.
One male victim is in critical condition and undergoing surgery, while the condition of the three other victims is stable, Robertson said.
Bourbon Street was packed with thousands of tourists and revelers celebrating the last weekend before the Mardi Gras (French for Fat Tuesday) when the shooting occurred. The name and other details of the victims are yet to be revealed.
Police said they are investigating the incident to identify the attackers and their motive.
"They're just piecing together what happened," Robertson said.
Witnesses told local media that there was commotion on a corner of Bourbon Street and they saw people screaming and running away.
"Everyone immediately started running and the cops immediately started running towards where people were running from," Patrick Clay, 21, an Louisiana State University student, told the New Orleans Times-Picayune. "I was with a group of about seven people and at that point we all just kind of grasped hands and made our way through the crowd as soon as possible."
Bourbon Street and the French Quarter are thronged by over a million people in the 12 days ahead of Fat Tuesday. Revelers, dancers, musicians and youngsters take part in the processions with colorful costumes and masks. Several parades with huge floats are a major attraction of the carnival and people throw beads, masks and small toys towards the revelers during the parades. During the carnival, authorities control the massive crowds on jam-packed streets on a horse patrol.
Floats and parades do not enter the French Quarter as the streets are too narrow for the floats to pass through. However, revelers head to the French quarter, which is famous for the strip clubs and pubs at the end of the parade.