ECB approval was expected given UniCredit's financial strength and a supervisory stance which is supportive of consolidation efforts, but it still marks an important step towards what could become Europe's biggest cross-border banking deal since the global financial crisis.

The European Central Bank has given UniCredit the green light to buy up to 29.9% of Commerzbank, the Italian bank said, adding it would likely wait until next year before deciding whether to pursue a full takeover.