LONDON, July 1 (Reuters) - Borrowing costs in Spain and Italy fell on Friday to their lowest levels since March 2015, extending this week's hefty tumble on hopes of further monetary stimulus from the European Central Bank to offset the fallout from Brexit.

Spain's 10-year government bond yield tumbled more than 10 basis points to as low as 1.108 percent.

The Italian 10-year bond yield fell to 1.037 percent , its lowest since March 2015.

(Reporting by Dhara Ranasinghe; Editing by Andrew Heavens)