The BBC's Cairo correspondent Yolande Knell said Mr Galloway had returned from Gaza, where the convoy arrived two days ago, and had been planning to head back to London.
But when he and his assistant returned to Egypt they learnt that seven other members of the convoy still in Gaza were due to be arrested on their return to Egypt.
Mr Galloway wanted to go back to accompany them out but it is understood the Egyptians would not allow him to return, bundled both men into a van and escorted them to the airport.
There has been much tension around the aid convoy after Egypt made it take a big detour, delaying its arrival. There were clashes with Egyptian police at a port close to the Rafah crossing, our correspondent said.
A spokeswoman for the convoy said police intervened when Mr Galloway and colleague Ron McKay arrived at the crossing.
"As soon as they emerged on to Egyptian soil, both men were forcibly pushed into a van, refused exit and told that they were leaving the country. They were then driven off in a police convoy."
She said Mr Galloway had been put on a plane bound for London.
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