* Pays S$100 million for the 5 pct stake

* Deal is Changi's largest acquisition to date

* Nomura advising Changi on the deal - source

(Adds details)

SINGAPORE, March 1 - Singapore's Changi Airport said on Monday it has acquired a 5 percent stake in Gemina S.p.A (GEMI.MI), the operator of Rome's two major airports, for S$100 million ($71 million), its biggest acquisition ever.

Gemina's Aeroporti di Roma owns the concession to operate Italy's largest airport group, which comprises Leonardo da Vinci Airport and Giovan Battista Pastine Airport.

Both airports serve the Italian capital and have a combined air passenger volume of 38.6 million in 2009, slightly higher than Changi's 37.2 million passengers last year.

With this investment, CAG becomes the first Asian operator to invest in a European capital city airport with a substantial strategic role, Changi CEO Lee Seow Hiang said in a statement.

Sources briefed on the deal said Changi hoped to secure consulting and management contracts from the two Roman airports, and could potentially be involved in the design of a new airport terminal in the Italian capital city.

Changi, which operates Singapore's main airport, has partnerships in China, India, Russia and the Middle East, and provides consultancy services to 20 airports in 10 countries.

It recently acquired a 26 percent stake in Bengal Aerotropolis Projects in India. It has a strategic partnership with Shenzhen Airport Group and owns a stake in Beijing Capital International Airport.

Singapore's finance ministry is in the process of injecting Changi into Singapore state investor Temasek [TEM.UL].

Nomura (8604.T) advised Changi Airport Group on the deal, the sources said. (Additional reporting by Saeed Azhar; Editing by Kevin Lim)