AMSTERDAM: Europe’s top regulator has warned Nokia not to try to become a “patent troll” after the Finnish company sold most of its cellphone-making business to Microsoft this year but retained its patent portfolio.

Joaquin Almunia said in a speech in Paris he had approved the $7.2 billion sale as not presenting problems on Microsoft’s side, but there is a danger Nokia will now attempt to “extract higher returns” from its patent portfolio. “In other words...behave like a patent troll, or to use a more polite phrase, a patent assertion entity.”

Almunia, in charge of competition at the European Commission, the executive arm of the European Union, warned he will open an antitrust case against the company if it attempts to take “illegal advantage” of its patents.

In a separate development, sources familiar with the matter said Nokia had offered to pay a 270 million euro ($369 million) deposit to Indian authorities to unfreeze assets in a tax dispute.

The Finnish firm has been trying to free up the assets, particularly its Chennai factory which is one of its biggest phone-making plants, ahead of the sale of its mobile phone business to Microsoft.

The offer comes on top of an earlier agreement to pay around 85 million euros, although Nokia hopes to eventually retrieve the payments if the tax dispute is resolved in its favor, one of the sources said on Monday.

The combined payment would exceed the income tax bill of 20.8 billion rupees ($338 million) demanded by local authorities in one of several tax disagreements involving foreign companies in India.

While Nokia has said it does not expect the dispute to affect its 5.4 billion euros deal with Microsoft, which is expected to close in the first quarter of 2014, a lengthy asset freeze could complicate matters by preventing the transfer of ownership in the Chennai plant.

An asset freeze would allow the facility to operate as usual but prevent a change of ownership. If it is still in place when the Microsoft deal is finalized, Nokia could briefly operate the plant as a contract manufacturer for Microsoft, but both companies are hoping to avoid this.

Nokia declined to comment beyond saying it was committed to getting its Indian assets unfrozen and “once again calls on the Indian government and tax authority to work with urgency toward a solution.”

The Delhi High Court is due to hear the case on Tuesday.