MILAN, Dec 20 (Reuters) - Italian aerospace and defence group Leonardo said on Monday it had signed a new ESG-linked credit line worth 600 million euros ($678 million), making half of the group's financing sources sustainable.

The credit line, which expires at the beginning of 2027, is aimed at refinancing bonds maturing in January 2022 and is linked to specific ESG (environmental, social and governance) indicators, including the reduction of CO2 emissions and the employment of women who graduated in scientific and technical studies.

"With the signing of this credit line, 50% of Leonardo's sources of financing are now ESG-linked," Leonardo CEO said in a statement.

Banco BPM, BNP Paribas, BPER, Crédit Agricole CIB, Intesa Sanpaolo, UniCredit were lead arrangers and bookrunners for the ESG loan, the group said.

($1 = 0.8854 euros) (Reporting by Francesca Landini Editing by Mark Potter)