Sixteen people have been injured after multiple gunmen opened fire on a crowded park in New Orleans, police say.

Key points: Police say 16 people injured in mass shooting in New Orleans

Police say 16 people injured in mass shooting in New Orleans Multiple shooters opened fire at park where hundreds of people had gathered, reports say

Multiple shooters opened fire at park where hundreds of people had gathered, reports say Wounded taken to hospitals in the area

Wounded taken to hospitals in the area Witnesses describe seeing man with a machine gun

New Orleans Police Department spokesman Tyler Gamble confirmed 16 people were injured at Bunny Friend Park in Upper Ninth Ward, but did not confirm whether all had gunshot wounds.

"We know, by speaking with some of the victims, that there were two groups of people shooting at each other," Mr Gamble said.

Asked whether gang activity was thought to be involved, Mr Gamble said it "was still too soon to say".

According to a police statement, 10 gunshot victims were taken to area hospitals by ambulance, and six more arrived at emergency rooms "via private conveyance."

Mr Gamble said each of the 16 victims suffered either a "direct gunshot wound" or a "graze wound" and all were listed in stable condition, though the full extent of their injuries was still to be ascertained.

Several hundred people were gathered in the park at the time for an unpermitted block party and the impromptu filming of a music video, according to police.

"Witnesses saw a man run with gun with an extended clip while another gunman was still shooting into crowd," journalist Meg Farris from CBS affiliate WWL tweeted.

The shooting happened about 6:15pm local time.

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The Times-Picayune newspaper quoted New Orleans Police Superintendent Michael Harrison as saying he believed multiple people had fired into the crowd of more than 300.

"I can't speak to the condition of all the victims," Superintendent Harrison said, but "no one has died at this time," the newspaper quoted him as saying.

Witness Cherie Brown told Storyful Newswire she heard "around 100" shots fired after letting her children play in the park.

"I thought it was a war going on outside," she said.

Three witnesses told the Times-Picayune they saw a man with a machine gun, and also heard more gunshots coming from within the crowd as he ran away.

Several people were lying on the sidewalk after the shooting, it said.

Video on the Times-Picayune's website showed paramedics attending to a number of injured people and loading a stretcher into an ambulance.

The park was holding the after-party of a large annual parade organised by the Nine Times Social Aide & Pleasure Club, the newspaper reported.

Katie Moore, a journalist for WWL, said no children were shot.

"No kids shot at Bunny Friend Park, but teenagers were," she tweeted.

Map Map of Bunny Friend Park in New Orleans

ABC/Reuters