The opening show of One Direction's London residency was blighted by technical difficulties.

The boyband performed the first of six concerts at the at O2 Arena on Thursday (24Sep15), but the gig came to an unexpected halt when the singers suffered sound problems.

They had to restart their song Night Changes three times, and even asked fans to sing the track themselves as sound engineers worked to fix the issues.

The pop stars said sorry for the delay, and Niall Horan explained to the crowd, "We've performed all over the world and this has never happened," before Harry Styles joked about the embarrassment, adding, "'We were caught with our pants down, we were exposed."

The issue was eventually fixed and they were able to continue with the set.

After the show, Niall tweeted an apology: "London... Thank you for tonight... First of 6 shows at that incredible arena... Sorry about the technical problems."

The band is set to play five more dates at the venue as part of the residency, which ends on 30 September (15).

The first O2 Arena show came just days after the pop stars thrilled fans with an intimate gig at London's Roundhouse on Tuesday night (22Sep15) as part of the Apple Music Festival, featuring an opening set from Little Mix.

During the Roundhouse show, Harry kept a close eye on his sister, who was in the audience with a date.

"I apologise if I seem a little bit distracted. My sister is on a date," he told the audience. "Behave yourself... I'm trying to keep an eye on her," while Liam Payne added, "We are all watching you."