NEW YORK, United States — Tiffany & Co.'s revamp is starting to pay off.

On Wednesday, the jeweller posted strong sales growth for last quarter, raised its profit forecast for the year and announced a share buyback plan of $1 billion. Worldwide same-store sales, a key retail metric, blew away analysts’ estimates last quarter, led by gains in North America and Asia. The shares jumped 7.8 percent in early trading.

Chief executive Alessandro Bogliolo is overhauling Tiffany to reverse a long sales slide. Hired last year, the former Diesel executive aims to woo a younger clientele by refreshing jewellery lines as he looks to generate hype for a 181-year-old brand that had grown stale. The revitalisation attempt includes redesigned stores and back-end improvements in procurement and technology operations.

Global same-store sales climbed 7 percent when holding currency constant, compared with the 2.6 percent growth projected by analysts, according to Consensus Metrix.

Bogliolo's jewellery renewal is just getting under way. Shoppers got their first look at creative chief Reed Krakoff's debut jewellery collection on May 1. The former top designer at handbag label Coach released a line of platinum bracelets and diamond necklaces that came with price tags from $2,500 to $790,000.

Tiffany has often relied on hit products to drive sales, but older styles from designers like Elsa Peretti and Paloma Picasso have remained top attractions rather than new lines. Krakoff hopes to change that.

By Kim Bhasin; Editors: Anne Riley Moffat, Lisa Wolfson, Cecile Daurat.