Kobe Bryant's wife offered a poignant portrait of her NBA superstar husband and their daughter on Monday at a packed memorial service for the two, who were among nine people killed last month in a helicopter crash in Los Angeles.

Speaking at times through tears, Vanessa Bryant praised her husband's devotion to their family as she addressed thousands of fans gathered at Staples Center to remember Bryant and 13-year-old Gianna.

"God knew they couldn't be on this Earth without each other," Vanessa Bryant said. "He had to bring them home to have them together. Babe, you take care of our Gigi."

The service took place at the downtown arena where Bryant played for the Los Angeles Lakers for the final 17 seasons of his two-decade NBA career.

Among the fans was Alyssa Shapiro, 27, of Huntington Beach, who said she was inspired to become a basketball player after watching countless Lakers games with her father.

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The family's love of the game - and Bryant's work in women's sports - prompted her to become a middle school girls' basketball coach. Her team had played Gianna's team and she would watch Bryant cheer for his daughter in the stands.

Holding homemade heart-shaped "Kobe" and "Gigi" signs, she said she went up to Bryant to introduce herself at a game.

"I just wanted to thank him for being such an inspiration to me," she said. "I grew up watching him on the screen ... It made me realise he's more than just that guy out on the court."

The concourse at the Staples Center was a sea of people dressed in the team colours of purple and yellow and others in black. On the scoreboard, the Bryant family's life flashed by in pictures: Vanessa and Kobe, Kobe and Gianna, the whole family in costumes, Gianna on the court, baby pictures of Gianna and her father.

Fans were given a programme containing photos, a purple KB pin and a T-shirt with photos of the father and daughter.

Also in the crowd was Bob Melendez, 72, who has been a season ticket holder for 40 years. After seeing Bryant play for the Lakers for years - including at his retirement game - Melendez said he could not imagine missing the memorial.

He wore a black number 24 jersey and Lakers jacket he bought for Bryant's final game.

"I'd never dreamed I'd be wearing this" at Bryant's memorial, he said.

Melendez was joined by friends Tom Ling and Rene Vega, who said his grandchildren and Bryant's children attend the same school. Bryant called Vega "Grandpa."

Ling, wearing a silver number 8 jersey, said the news of Bryant's death was initially too awful to accept.

"We didn't want to believe it," he said.

The service featured speakers reflecting on Kobe Bryant's effects on his sport and the world, along with music and retrospectives on Bryant's on-court achievements. Bryant became active in film, television and writing after he retired from basketball in 2016.

Michael Jordan, Magic Johnson and former Bryant team-mate Shaquille O'Neal were among the attendees at the "Celebration of Life" memorial.

Alyssa Shapiro, 27, of Huntington Beach, and her father Rick Shapiro, 55, standing outside Staples Center in Los Angeles before a public memorial for Lakers legend Kobe Bryant and his daughter, Gianna [Stefanie Dazio/AP Photo]

Bryant's family, dozens of sport greats and many major figures in Bryant's public life attended.

Money from ticket sales were expected to be given to the Mamba and Mambacita Sports Foundation, which supports youth sports programmes in underserved communities and teaches sports to girls and women.

Vendors sold flowers, Lakers scarves and commemorative newspapers and jerseys. Buses drove up and down Figueroa Street with their signs lit up with "RIP KOBE."

Business partners Donnell Dorsey and Ramon Acevedo slept along Figueroa Street on Sunday night to make sure they could claim a spot for their Lakers merchandise. Dorsey said he sold out of Bryant-related T-shirts and hats five times the day after the basketball superstar died.

On Monday, the duo sold framed photos and drawings of Bryant and Gianna for five dollars apiece, T-shirts and hats for $15 each and medallions for $25.

Dorsey said a friend told him about Bryant's death. "He was like, 'He's gone. Gone where?"

"I was, I guess you might say, numb," Dorsey said.

Vanessa Bryant speaks during a celebration of life for her husband Kobe Bryant and daughter Gianna in Los Angeles, California [Marcio Jose Sanchez/AP Photo]

Bryant played his entire 20-year NBA career with the Lakers, including the final 17 seasons at Staples Center, which opened in 1999. The five-time NBA champion's two retired jersey numbers - 8 and 24 - hang high above the arena where he became the third-leading scorer in league history until Lakers star LeBron James passed him on the night before Bryant's death.

Bryant's death caused an outpouring of grief across Los Angeles, where he remained the city's most popular athlete into retirement. Dozens of public memorials and murals have been installed around the sprawling metropolis, and thousands of fans gathered daily outside Staples Center to commiserate after the crash.

A private funeral was held for Kobe and Gianna Bryant in Orange County on February 7.

Also on Monday, Vanessa Bryant filed a wrongful death lawsuit against the company that operated the helicopter that crashed, saying the pilot was careless and negligent by flying in cloudy conditions and should have aborted the flight.

The lawsuit seeks general damages, economic damages, punitive damages and more, the Los Angeles Times reported.

Pilot Ara Zobayan was among the nine people killed in the crash.