* Purchase price just under 100 mln euros - sources
* Proceeds repay Alpine's bridge loan from FCC -source (Adds sources on purchase price, background)
VIENNA/FRANKFURT Aug 13 Private equity group Triton has agreed to buy the Alpine Energie unit of Spanish construction group FCC in a deal that sources close to the transaction said on Tuesday was worth nearly 100 million euros ($133 million).
Neither side gave financial terms in their joint statement.
Alpine Energie plans, sets up and maintains telecommunications, energy and traffic infrastructure. It employs about 3,000 people and has annual turnover of about 460 million euros, mostly in Germany, Austria and Switzerland.
FCC had kept Alpine Energie as a separate unit so it did not get swept into insolvency proceedings of its former parent Alpine, the Austrian construction group that FCC also owned.
FCC had used the unit as collateral for a 75 million euro bridge loan that it and another investor gave Alpine this year before it went bust. Proceeds from the Alpine Energie sale will repay that loan, one person close to the matter said.
What is left over will go to Alpine creditors, which include UniCredit unit Bank Austria and Erste Group, this person said.
Triton, with funds of more than 4 billion euros, invests in medium-sized businesses in northern Europe and Nordic countries. The Alpine Energie deal requires regulatory approval, it said. ($1 = 0.7523 euros) (Reporting by Angelika Gruber and Michael Shields in Vienna and Arno Schuetze in Frankfurt; Editing by Louise Ireland)