Shares in Spyker Cars, the Dutch car manufacturer, soared by more than 25% this morning after it made a new attempt to take control of Saab.

Luxury vehicle-maker Spyker presented an improved offer for Saab yesterday, and gave parent company General Motors until 10pm GMT tonight to respond.

Spyker shares jumped €0.47 to €2.18 (£1.93) this morning on the Netherlands stock market.

Victor Muller, chief executive of Spyker, said last night the new offer addressed all the stumbling blocks that emerged last week in its earlier talks with GM.

"We have made every effort to resolve the issues that were preventing the conclusion of this matter and we have asked GM and all other involved parties to seriously consider this offer," Muller said.

Union officials in Sweden urged GM to give Spyker's new offer serious consideration.

"I understand the frustration felt by everyone who is dependent on Saab, to be thrown between hope and despair is terrible," said Stefan Löfven, chairman of the IF Metall union.

Analysts said that today's share rally, which pushes Spyker's value up to £34m, was fuelled by speculation that the company could become profitable if it took control of Saab and turned it around.

GM announced last Friday that it would close Saab down, bringing 62 years of Swedish motoring history to an end. It has been trying to find a buyer for the loss-making division for most of 2009. GM said that it had no choice but to close Saab after earlier talks with Spyker failed to reach an agreement. The move would cost thousands of jobs in Sweden, and put thousands more at risk across Saab's network of UK dealerships.

Spyker's renewed interest in Saab has raised hopes that the carmaker could be saved. GM said last night that it had received several expressions of interest, but declined to comment further.