The surprise performance comes after Liam previously hosted his own concert in aid of the tragedy, when he took to the stage at Manchester's O2 Ritz on Wednesday.
However, the benefit concert wasn't enough to reunite Liam with his Oasis bandmate and brother Noel - whom he has been feuding with since the band split in 2009 - despite sources claiming there was a "definite chance" they would perform together.
An insider said: "There is a definite chance of this. There would be no better display of unity than them performing together."
Previously, Liam branded the terrorist attack as "outrageous".
He said: "It's outrageous. Just so sad. What can you do? It's just f***ing out of order. There are kids and people dying all over the world. And for what?
"I'd gone to bed early - about 10pm - then got up in the morning to a text from my other brother saying what had gone on and I put the TV on. It's just unbelievable."