Thousands of fans have gathered in Los Angeles to celebrate the life of Kobe Bryant and mourn the death of the NBA superstar and his daughter Gianna.

Bryant’s wife Vanessa provided a poignant portrait of her husband and their daughter at a memorial service for the pair, titled The Celebration of Life.

Her husband and teenage daughter were among nine people killed in January in a helicopter crash in Los Angeles.

Speaking at times through tears, Ms Bryant praised her husband’s devotion as she addressed 20,000 fans gathered at Staples Centre to remember Bryant and 13-year-old Gianna.

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

The service was held at the arena where Bryant played for the Los Angeles Lakers for 17 seasons of his two-decade NBA career.

The ceremony began with Beyonce performing her songs XO and Halo with dozens of backup musicians. Later, Alicia Keys performed Beethoven’s Moonlight Sonata, while Christina Aguilera sang Ava Maria.

After Jimmy Kimmel welcomed the crowd, Ms Bryant remembered the family’s life with Gianna and her three sisters and then eulogised her husband. They had been together since 1999.

“He was the most amazing husband,” she said. “Kobe loved me more than I could ever express or put into words. I was fire. He was ice. Vice versa at times. … He was my everything.”

The mourners included Lakers greats such as Jerry West, Kareem Abdul-Jabbar, Magic Johnson and Pau Gasol.

NBA commissioner Adam Silver joined Michael Jordan, Phil Jackson and dozens of current NBA players, including Stephen Curry, Kyrie Irving and Los Angeles natives James Harden, Russell Westbrook and DeMar DeRozan.

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Celebrities such as Kanye West, Kim Kardashian, Jennifer Lopez and Alex Rodriguez also attended.

Ms Bryant was followed on the podium by basketball stars Diana Taurasi and Sabrina Ionescu. Bryant was a passionate advocate for women’s basketball, and Gigi was a promising young player.

“If I represented the present of the women’s game, Gigi represented the future, and Kobe knew it,” said Ionescu, the Oregon star who was mentored by Bryant.

The concourse was a sea of people dressed in the Lakers’ colours of purple and yellow, with others in black. On the scoreboard, the Bryant family’s life flashed by in pictures.

The service began just hours after Ms Bryant sued the owner of the helicopter that crashed in the fog last month. The wrongful-death lawsuit claimed that the pilot, Ara Zobayan, was careless and negligent by flying in cloudy conditions.

The service was a chance for a grieving city and Bryant’s worldwide fans to reflect on his impact on his sport and the world while enjoying music and retrospectives on his on-court achievements. Bryant worked in film, television and writing after he retired from basketball in 2016.

A excerpt from the short film Dear Basketball – which won Bryant an Academy Award – played on the big screens at Staples to wrap up the public memorial.

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”.

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. He was only passed by Lakers star LeBron James on the night before Bryant’s death.

Bryant remained the most popular athlete in Los Angeles into retirement. Dozens of public memorials and murals have been installed, and thousands of fans gathered daily outside Staples Centre to commiserate after the crash.

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

-with AAP