Uh oh! Did the U.K.'s biggest boy band rivalry come to a head with physical violence?

According to reports, One Direction tried to flee a Burbank, Calif. recording studio when they learned that the Wanted were going to be present in the same building at the same time ... because 1D feared that the 'Glad You Came' singers were going to beat them up! So what went down?

When One Direction were rehearsing for their 'Saturday Night Live' performance on April 4, the 'What Makes You Beautiful' band's security team got wind that the Wanted were on their way to rehearse for their own 'American Idol' performance. Rumor has it all of 1D except Liam Payne were pretty terrified that the "tough guys" from the Wanted were going to start a fight with them following all of the tension and taunts in U.K. media between the groups.

One Direction decided to end their session early and jet their cute butts out of there, but before they could exit, the Wanted arrived. Yikes!

Thankfully, security teams for both bands met up to discuss the issue. When the Wanted's security team told the 'Lightning' singers about 1D's concerns, Max George took matters into his own hands and made a beeline for One Direction's studio, busting in and ... giving Payne a hug.

Sources told TMZ that all the guys had a good laugh about it and were great sports -- except One Direction member Louis Tomlinson, who wouldn't go anywhere near any of the guys from the Wanted.

We wonder what personal beef there is between Tomlinson and the lads, but we're glad most of them get along well! Is a joint tour or collaboration (perhaps with Justin Bieber) in order?