By Kirsti Knolle and Anne Kauranen

BERLIN/HELSINKI (Reuters) -Germany on Wednesday agreed to nationalise Uniper, raising the bill to rescue the gas importer to 29 billion euros ($28.7 billion) amid an escalating energy crisis that shows just how much Europe's top economy has relied on Russian fuel.

The deal brings the total cash pumped into Germany's three biggest Russian gas importers - Uniper, former Gazprom unit Sefe and EnBW's VNG division - to at least 40 billion euros.

Nationalising Germany's largest importer of Russian gas is the second move in a week by the government to take control of an energy business and is part of a wider European response to the winter crisis, including France taking over EDF.

Germany last week also took control of a Russian-owned oil refinery, which supplies 90% of the capital's fuel, putting a Rosneft unit under the trusteeship of the industry regulator and taking over the Schwedt plant.

Uniper, whose shares closed 25.3% lower, burned through its cash buying alternative supplies after Moscow cut gas flows to Germany, triggering an initial 15 billion euro state rescue package in July.

But as with other European energy companies hit by soaring gas prices, it became clear the bailout was not enough to cover Uniper's deepening losses. Germany will now inject yet more cash, partly by buying out Finnish utility Fortum's 56% holding for 500 million euros, or 1.70 euros per share.

'CLEAN BREAK'

Fortum shares ended the day up 9.5% on the news, with analysts at Bernstein saying the deal "allays investor fears and provides a clean break" for the Finnish group.

After completing a capital increase and the Fortum share buy, which excludes the Finnish firm's subscription rights, Germany will hold 99% of Uniper, its economy ministry said.

"The state will - that's what we're showing now - do everything possible to always keep the companies stable on the market," German economy minister Robert Habeck told reporters.

Berlin has said it would review an application earlier this month by VNG which asked the government for aid to stay afloat.

Habeck also said Berlin will impose a gas levy on consumers as planned from the start of October to help importers with the additional costs of replacing Russian gas.

However, there will be an analysis of whether it is in accordance with German law after the nationalisation of Uniper, which could take about three months, he said.

German Finance Minister Christian Lindner meanwhile said that the levy was finalised and there would be no further assessment, apparently contradicting Habeck.