People slammed Will.i.am as he called out to London at a concert held for the victims of a Manchester attack.

Fans were baffled as he asked "what's up London?" as he came out on stage, and then repeatedly shouted London while he performed with Ariana Grande at One Love Manchester.

Black Eyed Peas teamed up to sing Where is the Love? in tribute to the victims of the Manchester attack.

But the focus was on Will.i.am's apparent mistake.

People took to Twitter to complain, but he responded saying it was on purpose in recognition of the London Bridge terror attack on Saturday.

Three terrorists mowed down pedestrians on the bridge before wielding knives and stabbing people in Borough Market.

Will.i.am said that was what he was referring to when he called out to London, and it wasn't a slight at Manchester.

One Love Manchester is being held in the city's Old Trafford ground, just two weeks after a suicide bomber targeted Ariana Grande's concert held in Manchester Arena killing 22 and injuring more than 100 fans.

(Image: BBC)

Ariana said she was "broken" by news of the bombing at her concert - and also spent time speaking to the families of those killed.

Police confirmed the One Love Manchester gig will go ahead despite the terror attack in London on Saturday night, where seven people died and dozens more were injured by terrorists wielding knives.

“As much as Ariana wants to perform the track, it will be difficult for her to keep her emotions in check," a source told The Sun. “She may well get choked up while she is singing so she will begin the song, then the Peas will join in to help her."

(Image: BBC)

Their duet wasn't the only song that hit home, as Robbie sang Angels, as well as a version of Strong, with altered lyrics to reference the attack.

The song included: "Manchester we're strong, we're strong, we're still singing our songs, our songs."

The concert is broadcasting to 50 countries and will air on BBC One at 6.55pm.

Organisers hope the benefit gig will raise £2m for victims of the attack.