LINZ, Austria (AFP) - Unseeded Czech Petra Kvitova upset Agnieszka Radwanska in the semi-finals of the WTA event here, winning 6-3, 6-2 to set up a final against either Flavia Pennetta or Yanina Wickmayer.

Radwanska, the second seed from Poland who was playing her 65th match of the season and her 14th in three weeks, looked flat against an aggressive opponent who struck some stinging returns and moved the ball around well to leave Radwanska out of position.

Radwanska was in trouble right from the first game as Kvitova took a 1-0 lead on her fourth break point. And although Radwanska levelled at 1-1, she dropped her next service game at love.

Three double-faults in her third service game then helped Kvitova to a third break and a 4-1 lead.

The Czech, who beat world number one Dinara Safina to reach the fourth round of the US Open last month, failed to serve out the set at 5-2, but she earned a fourth break at 5-3 when Radwanska hit a forehand wide down the line.

Kvitova maintained the pressure in the second set, breaking to lead 2-0 after a fine return set up a winning volley.

Another volley saved a break point in the next game, and she went on to tie up the match in an eight-deuce final game, clinching victory on her seventh match point.

The second semi-final, between top seed Pennetta of Italy and Belgian third seed Wickmayer, is scheduled for later on Saturday.