By Kathy Finn

NEW ORLEANS (Reuters) - A weekend shootout that wounded 17 people, including a 10-year-old boy, in a New Orleans park appears to be gang-related, city officials said on Monday, as they urged hesitant witnesses to come forward with information about the suspects and a motive.

The incident unfolded Sunday evening at a playground in the city's Upper 9th Ward where a crowd of as many as 500 people had gathered for a block party and the filming of a music video, police said.

Two groups began shooting at each other "with hundreds of people in the way," New Orleans Police Superintendent Michael Harrison told reporters, adding automatic weapons were fired.

Eleven of the injured are under age 21. Though most of the victims have been discharged from hospitals, one may never walk again, said New Orleans Mayor Mitch Landrieu.

"I'm outraged at an unbelievable level ... for those who decided everybody's life in that park did not matter,” Landrieu said.

No arrests have been made. With tips about the shooting slow to emerge, the mayor pushed for witnesses to tell law enforcement what they had seen.

The city also planned a rally for Monday evening at Bunny Friend Park to urge citizens to take back their streets.

The shooting at the park followed a community "second line" parade that ended a few blocks away earlier in the day, police said.

A large crowd assembled in the park for an unauthorized block party and the impromptu music video filming when gunfire erupted. The groups involved in the shooting immediately fled from the scene, police said.





(Additional reporting and writing by Colleen Jenkins; Editing by David Gregorio and Alan Crosby)