BERLIN — Commerzbank AG said Thursday that it will get euro10 billion ($13.5 billion) in fresh capital from a German government rescue fund, a deal that will give the government a 25 percent stake.

The Frankfurt-based bank, Germany's second-biggest, said the new injection would increase its core capital ratio to 10 percent. But Commerzbank shares closed down 13.8 percent at euro5.25 in Frankfurt after the announcement.

"We are weatherproofing our bank for an economically stormy environment," Commerzbank CEO Martin Blessing said in a statement. "This will enable us to fulfill our responsibility to offer loans to the German economy and to ensure we will continue to be a reliable partner for our clients."

Commerzbank already had received euro8.2 billion from the government's fund, which was put together last fall and is worth as much as euro500 billion.

The new injection will leave the government with a holding of 25 percent plus one share, and thus with a blocking minority that would allow it to veto major decisions.

The move comes as Commerzbank moves forward with plans to acquire Dresdner Bank AG from insurer Allianz SE.

Commerzbank said that, under Thursday's deal, Allianz is to boost Dresdner Bank's capital by euro1.45 billion once the transaction is complete by taking over collateralized debt obligations from the bank.

Finance Ministry spokesman Torsten Albig said Thursday's deal was "a strong signal for a strong Commerzbank."

He said in a statement that it showed the government is taking "responsibility for one of the large German players on the financial market."

Allianz shares were down 5.4 percent at euro66.67.