Sagan at the double, Quintana still leads

Slovakian cyclist Peter Sagan of Bora-Hansgrohe celebrates as he crosses the finish line to win the 69th edition of the Kuurne-Brussels-Kuurne on February 26, 2017

World champion Peter Sagan underlined his form a week before the Milan-San Remo classic by winning the fifth stage of Tirreno-Adriatico on Sunday, his second of the Italian stage race this week.

Colombia's Nairo Quintana, of the Movistar team, retained the race leader's blue jersey following his summit-finish win on Saturday's fourth stage which forced ailing Italian rival Fabio Aru (Astana) to pull out with bronchitis on Sunday morning.

Bora team rider Sagan, a powerful one-day rider who can sprint with the best in the bunch, had dominated the field to win Friday's third stage.

And the flamboyant Slovakian, known for his garish outfits and performing one-handed 'wheelies' when riding up the climbs of some of Europe's top races, took his second win of the 2017 edition of the race with a defiant, uphill sprint in Fermo.

Frenchman Thibaut Pinot (FDJ) finished in second place with Slovenian Promoz Roglic (Lotto-NL) claiming third from a drastically reduced bunch after 201 km of racing from Rieti.

Milan-San Remo, known affectionately as 'La Primavera' (The Spring), is the opening one-day classic of the season and is held on March 18 and Sagan will line up looking for his maiden win.

Quintana, meanwhile, looks set to claim overall victory if he can survive until Tuesday's seventh and final stage.

The diminutive Colombian climbing specialist holds a 50sec lead on Pinot. The sixth stage on Monday is expected to finish in a bunch sprint that could see Sagan bag his hat-trick, while Tuesday's final stage is an individual time trial.