Image copyright AP Image caption Stevie Wonder and Tori Kelly teaming up for the Prince/Apollonia duet from Purple Rain, Take Me With U

Stevie Wonder, Jennifer Hudson, Roots, Erykah Badu and Sheila E were among the stars who performed tributes to Prince at the Black Entertainment Television (BET) Awards in Los Angeles.

Grey's Anatomy actor Jesse Williams received a standing ovation as he accepted the humanitarian award.

He gave what the Washington Post called "one of the most memorable speeches in award show history".

Samuel L Jackson was awarded the lifetime achievement award.

He praised Williams in his acceptance speech, calling him "the closest thing I've heard to a 1960s activist".

Image copyright Reuters Image caption Jesse Williams is best known for playing Dr Jackson Avery on Grey's Anatomy

Image copyright Reuters Image caption Samuel L Jackson was given his Lifetime Achievement Award by director Spike Lee

In Williams's speech he demanded equal rights and called for an end to police brutality against black people and white appropriation of black culture.

"A system built to impoverish, divide and destroy us cannot stand if we do," he said.

"We know that police somehow deescalate, disarm and not kill white people every day so what's going to happen is we're going to have equal rights and justice in our own country or we will restructure their function and ours."

"That brother is right and he's true," said Jackson, as he picked up his award.

"When you hear what he said, make sure you vote and you take eight more people with you to vote, OK? Don't get tricked like they got tricked in London!" he said, seeming to refer to the EU referendum.

Another political moment saw R&B artist Usher performing in a shirt which had Don't Trump America written on it.

Image copyright Reuters Image caption Jennifer Hudson sang Purple Rain accompanied by Stevie Wonder on piano and Tori Kelly on guitar

The Prince tributes were started by Erykah Badu who sang The Ballad of Dorothy Parker from Sign O' the Times.

Stevie Wonder and Tori Kelly teamed up for the Prince/Apollonia duet from Purple Rain, Take Me With U.

They were then joined on stage by Jennifer Hudson who sang the song Purple Rain.

Janelle Monae performed Kiss, Delirious and I Would Die 4 U, Bilal sang The Beautiful Ones and Maxwell sang Nothing Compares 2 U.

The show finished with Prince collaborator Sheila E leading a 10-minute montage of Prince songs.

She was joined on stage by actor Jerome Benton, who starred in the film Purple Rain, and Prince's ex-wife Mayte Garcia.

They ended the show by raising a purple guitar in the air while flower petals fell from the ceiling.

Image copyright Reuters Image caption Beyonce and Kendrick Lamar performed in a pool of water

Beyonce opened the show with a surprise performance of her song Freedom with Kendrick Lamar, dancing in a pool of water.

She won video of the year and the viewers' choice award for her song Formation but had already left the ceremony to catch a flight to London for a concert so her mother Tina Knowles accepted the award on her behalf.

"I want to thank, first of all, her husband and her daughter," she said.

Other winners included Taraji P Henson and Michael B Jordan, who won the acting awards.

Drake won best male hip hop artist and best group with rapper/singer/producer Future, but was not at the ceremony to accept the awards.

Newcomer Bryson Tiller beat Chris Brown and The Weeknd to win best male R&B/pop artist and also won best new artist.

Skepta won the best international UK act.

Muhammad Ali was also remembered at the ceremony by his daughter and Jamie Foxx, who starred in the 2001 biopic about the legendary boxer's life.

The award show airs in the UK on BET on Tuesday at 2100 BST.