LONDON, Dec 7 (Reuters) - Oil flow along the UK's Forties oil pipeline which carries the crude that usually sets the global Brent benchmark has been reduced after a leak was detected and by a separate issue at its Kinneil plant, pipeline operator Ineos said.

The size of the flow reduction was not immediately clear. A trade source said, however, that it was not large and loadings of Forties crude had not been affected.

"The operational pressure of the pipeline had been marginally reduced. However, rates were reduced mainly because of the issue at Kinneil, which is now restarting," Richard Longden of Ineos said via email.

Ineos said in a statement earlier on Thursday it was repairing the pipeline and that its Kinneil plant was flaring gas as a result of being re-started.

(Reporting by Alex Lawler; Editing by Mark Potter)