HOUSTON - Nineteen people were injured Sunday when gunmen opened fire at a Mother's Day parade in New Orleans in the US state of Louisiana, police said.

The victims were marching in what is known as a second line parade, which is common in New Orleans, when the shooting occurred at about 1:45 pm local time at an intersection, the local news website NOLA.com quoted Police Superintendent Ronal Serpas as saying.

About 12 people were initially said to be injured, but the number was revised to 19 as more victims continued to forward, Serpas said.

It appeared "two or three people," for an unknown reason, started shooting at the crowd, Serpas said.

Ten adult men, seven adult women, a 10-year-old boy and a 10-year-old girl were struck by bullets. Both of the child victims had graze wounds to the body and were in good condition, while a man and a woman were reported to be in surgery Sunday evening.

Many of the victims were grazed, some by bullets that ricocheted, said police spokeswoman Remi Braden. "At this point, there are no fatalities, and most of the wounds are not life-threatening," Braden said in an email.

Authorities saw three people running away from the scene immediately after the shooting. One suspect was described as a man aged between 18 and 22.

"Detectives are conducting interviews, retrieving any surveillance video in the area and, of course, collecting all evidence," said Braden.  "This is an extremely unusual occurrence, and we're confident that we will make swift arrests."

New Orleans Mayor Mitch Landrieu had urged anyone with information about the incident to come forward.