UPDATE 1-Finmeccanica buys 25 pct of Russian jet maker

* Buys 25 percent of Sukhoi Superjet 100 maker

* Signs other deals in Russian business mission

(Adds details, shares)

MILAN, April 7 (Reuters) - Italian aerospace and defence group Finmeccanica SpA (SIFI.MI) has bought 25 percent of the Russian maker of the Sukhoi Superjet 100 as part of a series of deals coinciding with a business mission in Russia.

Finmeccanica said on Tuesday its Alenia Aeronautica unit had bought 25 percent plus one share in Sukhoi Civil Aircraft Corp (SCAC), which makes the regional jet whose first customer is Russia's Aeroflot-Russian airlines (AFLT.MM).

No financial details were available.

The Superjet 100 has orders for 98 aircraft, Finmeccanica said.

Finmeccanica also said it had agreed to form a consortium with state-owned Russian Technologies to work together in the security sector.

And the group's Ansaldo STS (STS.MI) unit and Russian Railways unit NIIAS signed a deal worth about 7.5 million euros ($10.1 million) to test a railway signalling system.

"The contract ... lays the groundwork for further company initiatives on (Russia's) railway lines with an estimated value of more than 200 million euros in the next few years," Finmeccanica said.

Finmeccanica shares were up 1.4 percent to 9.67 euros by 0901 GMT, after falling in early trade after news of the proposed cancellation of a U.S. helicopter contract.

Ansaldo STS was down 0.6 percent at 11.08 euros, while the the DJ Stoxx index of industrial goods and services .SXNP was down 1.4 percent.

(Reporting by Danilo Masoni; Editing by Erica Billingham)

($1=.7389 Euro)