"I am surprised it did not come to light earlier," Karel Bruckner was quoted as saying by BBC sport late on Monday.

"We have tried to keep our promise to keep quiet but I must now admit that Tomas is undergoing medical tests."

The 25-year-old Rosicky is under contract with Bundesliga side Borussia Dortmund till 2008.

Arsenal manager Arsene Wenger said earlier this week that he is planning two major signings in the summer without revealing the names of his targets.