Avista Capital Partners and Cinven are among four private equity firms bidding for Thomson Reuters Corp's trade and risk management software business, Kondor, people close to the matter said.

Buyout shops Bridgepoint and Montagu have also advanced to the second round of the auction of Kondor, which could fetch between $600 million and $650 million, they said.

That range is higher than previous media reports, which had pegged Kondor's value at about $500 million.

Thomson Reuters hired Barclays Capital to sell Kondor and kicked off the process in June. A number of corporate buyers initially expressed interest, but had dropped out by the second-round bids, which were due on July 22.

Kondor, part of Thomson Reuters' global risk management division, provides trade and risk software as well as liquidity risk systems for treasury and cash management operations. Kondor's main competitors include Misys, SunGard and French software solutions company Murex.

Thomson Reuters said in April it expected to raise about $1 billion from the sale of its enterprise risk management and investment accounting software businesses, among other units.

Chief Executive Tom Glocer said the proceeds would be reinvested in the core business.

Final-round bids for Kondor are expected by mid-September, one of the sources said.

Thomson Reuters, as well as Cinven, Bridgepoint and Montagu, declined to comment. Avista was not immediately available for comment..

(Additional reporting by Isabell Witt in London; Editing by Ted Kerr)