UPDATE 1-BP's UK Unity platform to shut for 3-4 days

(Updates with length of outage, recasts)

LONDON, July 16 (Reuters) - BP (BP.L) is to shut its UK North Sea oil and gas Unity Riser Platform riser on Aug. 1 for 3-4 days for routine summer maintenance, a spokesman said on Friday.

The Unity Riser Platform links the Bruce, Scott, Nelson, Britannia, and Graben Area oil and gas fields to the main Forties oil line, the BP website showed. Last year, work on the platform lasted around a day.

Britannia and Bruce are large gas fields, producing 261 and 134 million cubic metres of gas in March 2010 respectively, according to government figures. Gas is transported from the fields to the St. Fergus terminal in Scotland. (Reporting by Kwok W. Wan; editing by William Hardy)