Saturday's shootings, plus the fatal stabbing Sunday night, brought this year's murder toll to 53, raising fears that violence was back on the rise in a city plagued by violent crime before Hurricane Katrina drove residents away last year.
Saturday's incident was one of the bloodiest in this city's turbulent history.
Nagin asked the governor to send up to 300 National Guard troops and 60 state police officers to patrol the city.
In addition to requesting help from the state, the city council said it would consider increasing overtime available for police and pay for more officers and street patrols.
"If we don't have wind knocking us down, we have shooters knocking us down, and that's unacceptable," said City Council President Oliver Thomas.
Cynthia Willard-Lewis, who represents predominantly black eastern New Orleans, said a big part of the solution will be getting young people off the streets and into caring environments such as schools.
She suggested opening schools after hours but didn't say how that could have prevented Saturday's 4 a.m. shooting.
"We're looking forward to the day when ... this city returns to being one of the safest cities in America," Nagin said.
The five shooting victims, ranging in age from 16 to 19, were gunned down early Saturday morning on a street in the Central City neighborhood just outside the central business district.
Authorities are searching for one or more suspects in the most violent crime reported in the slowly repopulating city since Hurricane Katrina hit last August.
Investigators believe the shootings were drug-related or a retaliation attack, Police Capt. John Bryson said. A semiautomatic weapon was used and "multiple, multiple rounds" were fired, he said.
"I think the motivation we're looking at is pretty obvious," Bryson said. "Somebody wanted them dead."
Three of the victims were found in a sport utility vehicle rammed against a utility pole and two were found nearby on the street. It was not immediately known if any of them were armed.
The victims were identified as Arsenio Hunter, 16; Warren Simoen, 17; Iruan Taylor, 19; Reggie Dantzler, 19; and Marquis Hunter, 19, said John Gagliano, the chief investigator for Orleans Parish Coroner Frank Minyard. The Hunters are believed to be brothers or cousins, authorities said.
Bryson said he could not remember the last time five people were killed in one incident, before or after Katrina.