General Motors is engaged in due diligence on about 10 bidders for Saab, after the first round of bids for the Swedish brand attracted Chinese automakers, European investor groups and private equity firms, a media report said.

The Saab auction process is being run independently of GM's efforts to sell other European assets including Opel, a source told Reuters, adding that GM has until the end of June to sell the Swedish unit.

China's Geely Automobile Holdings is one of the bidders for Saab, another source told the news agency.

Some Geely executives toured Saab's production and R&D facilities in Sweden last month, and were given presentations by the automaker's management team, the source said.

GM has given management presentations and tours to all of the bidders in the last month, both sources told Reuters.

GM said in February it would like the brand to become an independent business by 2010 and Saab subsequently filed to reorganise under court protection in Sweden, in a process similar to Chapter 11 bankruptcy protection in the US.

Though Fiat has said it wants to merge its car unit with GM's European operations, which include Opel and Saab, to create the world's second-largest automaker after Toyota, it did not bid in the first round of the Saab auction, both sources told Reuters.

Fiat said on Wednesday it had spoken with the Swedish government about buying Saab, and GM in turn responded by saying it would welcome any talks with Fiat.