Manchester United fans have reacted furiously to their side selling highly-rated defender Lee O’Connor to Celtic.

Celts swooped for the Irishman, 19, last night before the transfer deadline passed and got their man on a four-year deal.

The Hoops also tied up Man City kid Jeremie Frimpong and Greg Taylor, taking their summer recruit number to 11.

Their latest name O’Connor, though, left Red Devil’s supporters gutted at the thought of losing a kid with bags of potential.

And hundreds took to social media last night to vent their rage - demanding their club insert a buy-back clause.

One slammed: “United are actually selling Lee O’Connor to Celtic.

“Jesus christ, who is making these decisions? How are you letting one of our best prospects go for next to nothing.

“We better insert a buy back clause”.

Another fumed: “If Lee O'Connor does go to Celtic on a permanent, there better be some sort of buy-back clause involved.”

One said: “Sad to see a youngster with so much potential leave, but its definitely a great move for him!”

A fourth moaned: “Can’t believe we’ve let Lee O’Connor go. Smashing player with huge potential.”

O’Connor joins his Irish under-19s teammate Jonathan Afolabi in the Hoops ranks.