Polish teenager Agnieszka Radwanska stunned top-seeded Russian Elena Dementieva 7-5, 6-2 in the quarter-finals of the Luxembourg Championship on Friday -- her second big shock in as many days.

A day after ousting an injured Venus Williams, 17-year-old Radwanska took advantage of seven double faults from Dementieva to reach her first WTA Tour semi-final.

In the semi-finals she will play Italian fifth seed Francesca Schiavone, who outclassed third seed Patty Schnyder 6-1 6-1.

Dementieva led by an early break but the 95th-ranked Radwanska hit back, breaking in the 12th game to take the opening set.

The Pole raced 3-0 ahead in the second set and although Dementieva broke back, Radwanska clinched victory by breaking her opponent for the seventh time in the match.

On a bad day for the Russians, fourth seed Dinara Safina also went out, losing 6-4, 6-3 to Czech Kveta Peschke.

Peschke will meet unheralded Ukrainian Alona Bondarenko in the last four after the 22-year-old ousted France's Nathalie Dechy 5-7, 6-4, 6-0.