FCC, which is partly owned by Mexican tycoon Carlos Slim, has been dealing with high debts for several years following a 2008 property market crash in Spain which sent thousands of developers to the wall and brought the firm close to bankruptcy.

Slim, who earlier this month launched a full takeover bid for FCC, has pushed for a drastic debt-reduction plan since he first invested in the group two years ago.

The source said FCC had agreed with a dozen banks to repurchase between 380 million and 390 million euros of high interest bearing debt at a discount of more than 15 percent.

The debt carried an interest rate of around 5 percent and was seen as one of the last obstacles to complete FCC's financial turnaround.

FCC declined to comment on the move, which had first been reported by Spanish business newspaper Cinco Dias.

(Reporting by Robert Hetz; Editing by Julien Toyer and Alexander Smith)