It's been reported Justin Bieber was spotted at a Hillsong United concert in Inglewood, California on Thursday, and he was reportedly very emotional when he left The Forum arena.

Although it is unclear what brought it on, it would not be the first time that the pop star was moved to tears during worship.

Attendees at Thursday's concert took to Twitter to report Bieber's attendance, and his emotional state.

"At the Hillsong United concert and Justin Bieber is sitting right in front of me OMGGGGGG," one person wrote.

"Saw Justin Bieber at the Hillsong United Concert," another confirmed.

Another Twitter user said the singer was in tears when he left the venue.

"So justin bieber came to the Hillsong concert and came out crying," @daaa_seee tweeted.

Bieber is a regular at Carl Lentz's Hillsong Church in NYC, and often shares tweets and pictures demonstrating his friendship with the pastor.

Last year, the 20-year-old admitted that one of Lentz's sermons had hit an emotional chord.

"Love to my guy @carllentzNYC for the amazing sermon at church this morning," he tweeted. "Love you man. I broke down today. Thank [you]."

In June, the star was reportedly baptised by Pastor Carl in a bathtub after requesting a private baptismal ceremony, and has also shared clips of Lentz's sermons to his over 56 million Twitter followers.

Lentz, 34, said his relationship with Bieber is about love and acceptance.

"With Justin, I tell people grace and acceptance does not mean approval," he told CBN.

"I can accept you as a human being and not approve of your actions. That's how we've been loved. We love because we were first loved.

"With Justin, it's not my job to be his police officer. It's my job to be a friend to him, and that's all I am."

Bieber was also spotted at Los Angeles' City Church in August, when he attended Bible study with off-again girlfriend Selena Gomez. Bieber also counts Pastor Judah Smith, who heads the church's Seattle location, a spiritual mentor and a friend.