Wal-Mart Stores has announced a $15 billion share buyback programme at its annual meeting as the world's largest retailer faces increasing scrutiny from investors over how it has handled allegations of bribery in its Mexican operations that surfaced a year ago.

It brought the usual star power to its annual shareholder meeting, with X-Men and Les Miserables star Hugh Jackman hosting and singer John Legend entertaining.

But the festivities took a serious turn as shareholders in the audience stood to make proposals related to safety in Bangladeshi factories, Wal-Mart's Mexican bribery scandal and executive salaries.

The company is facing pressure to increase its oversight of factory conditions abroad following a building collapse in April in Bangladesh that killed more than 1,100 garment workers. The discounter, based in Bentonville, Arkansas, is also under scrutiny for how it treats its workers.-Reuters