UniCredit was able to buy 4.5% of Commerzbank from the German state because the government trusts the Italian bank, its CEO said in a newspaper interview, ruling out any "aggressive" moves such as an unsolicited buyout bid.

Analysts have welcomed the move by UniCredit, particularly because a tie-up between the two banks might spur more M&A activity in Europe's banking sector.

UniCredit SpA has demonstrated at its existing German unit that it can cut costs in the country, which bodes well for its potential plans for Commerzbank AG, analysts at KBW wrote in a note.