Germany on Friday agreed to bail out Uniper with a 15 billion euro ($15.24 billion) rescue deal, as the embattled energy company becomes the first major casualty of Russia’s natural gas squeeze.

The package will see the German state take a 30% equity stake in Uniper. The company’s shares initially rose when the deal was announced, before falling sharply. They were trading more than 21% lower an hour later.

Uniper was the first energy company in Germany — Europe’s largest economy — to sound the alarm over soaring energy bills, and submitted a bailout application for government support earlier this month. As Germany’s biggest importer of gas, it has been hit hard by vastly reduced flows via pipelines from Russia, which have sent prices soaring.

In a statement, Finnish majority-owner Fortum said Uniper and the German government had agreed on a “comprehensive stabilisation package” to provide it with financial relief.

“We are living through an unprecedented energy crisis that requires robust measures. After intensive but constructive negotiations, we found a solution that in an acceptable way met the interest of all parties involved,” Fortum’s president and CEO, Markus Rauramo, said in the statement.

“We were driven by urgency and the need to protect Europe’s security of supply in a time of war.”

Following the bailout, Fortum will own a 56% stake in Uniper — down from around 80% before the deal.

The German government is ready to provide further support if Uniper’s losses — as a result of the gas squeeze — exceed 9 billion euros, Fortum added.

Russian gas supplies to Europe have fallen since its unprovoked invasion of Ukraine earlier this year — and the subsequent sanctions placed on Moscow by the West.

Uniper has received only “a fraction of its contracted gas volumes” from Russian gas giant Gazprom since mid-June, according to Fortum, meaning it has had to buy gas at much-higher spot market prices. This has had severe consequences for Uniper’s financial position, Fortum added.

The front-month gas price at the Dutch TTF hub, a European benchmark for natural gas trading, was around 5% higher Friday at 164 euros per megawatt-hour. Prices are up more than 650% over the last year.

Last week, Uniper said it was already having to draw down gas from storage facilities, reducing supplies needed for winter. In a statement to CNBC, the company said that reducing gas volumes from its own storage facilities was necessary “in order to supply our customers with gas and to secure the Uniper’s liquidity.”

— CNBC’s Sam Meredith contributed to this report.