UniCredit's acquisition of a 4.5% stake in Commerzbank from the German government causes the bank's shares to increase by 20%.

• On Wednesday, Commerzbank's shares rose on market open following the acquisition of a 4.5% stake in the Frankfurt-based lender by Italian bank UniCredit from the German government.
• The sale of approximately 53.1 million shares, or a 4.49% tranche of its 16.49% total shareholding, by the German government in Commerzbank for around 702 million euros ($775 million) marks the first step in Berlin's exit from its position in the German lender.
• Commerzbank announced that UniCredit had acquired a 9% stake in the bank, with half of this shareholding coming from the government.

On Wednesday, Commerzbank's shares rose on market open following the acquisition of a 4.5% stake in the Frankfurt-based lender by Italian bank UniCredit from the German government.

Frankfurt-listed Commerzbank stock was up 20.31% at 12:54 p.m. London time.

The sale of approximately 53.1 million shares, or a 4.49% tranche of its 16.49% total shareholding, by the German government in Commerzbank for around 702 million euros ($775 million) marks the first step in Berlin's exit from its position in the German lender.

Despite being in a reduced 12% position, the German government remains Commerzbank's largest shareholder. Since injecting 18.2 billion euros to rescue Commerzbank during the 2008 financial crisis, Berlin has held its stake in the lender. As of last week, around 13.15 billion euros of that sum has been repaid.

Eva Grunwald, managing director of the federal finance agency, stated that Commerzbank's successful stabilization marks the completion of the first partial sale of the investment and the federal government's exit.

Commerzbank announced that UniCredit had acquired a 9% stake in the bank, with half of this shareholding coming from the government.

UniCredit will submit regulatory filings for authorization to potentially exceed 9.9% of Commerzbank if necessary, according to the bank. The Milan-listed stock of UniCredit was up nearly 0.5% at 12:55 p.m. in London.

"Commerzbank acknowledged the acquisition of an equity stake in itself by UniCredit, which was announced this morning. This demonstrates the progress made by Commerzbank and its current position. The management and supervisory board of Commerzbank will continue to act in the best interest of all shareholders and key stakeholders, including employees and clients."

An extraordinary board meeting has been scheduled by Commerzbank's supervisory board at 5 p.m. local time to discuss UniCredit, according to board member Stefan Wittmann, who shared this information with Reuters.

CNBC has approached Commerzbank for comment over the meeting.

On Wednesday, Commerzbank announced that Manfred Knof, its chief, will fulfill his contract but not seek renewal after December 2025. The bank will initiate the process of finding a successor.

Tying up

Some analysts believe that the recent stake transaction has sparked speculation about whether UniCredit, which already operates in Germany through HypoVereinsbank, will acquire Commerzbank to establish a dominant position in the German banking market.

Earlier this year, rumors circulated that Deutsche Bank, Germany's largest lender, might join forces with a domestic competitor. However, in January, Deutsche Bank CEO Christian Sewing stated that mergers and acquisitions were not a priority for his group at the time, dismissing the possibility of a fusion.

In contrast to UniCredit's recent activity in mergers and acquisitions, including its acquisition of Belgian digital bank Aion and its cloud platform Vodeno for 370 million euros in July, the bank reported a record first-half performance and a 6% annual growth in net revenues to 6.3 billion euros in the second quarter.

CNBC has reached out to UniCredit for comment over potential takeover intentions.