SNC-Lavalin Group Inc said on Friday it has bought a 48 percent stake in a Russian engineering company, a deal the Canadian company hopes will help it become a leader in that country's oil and gas market.

Financial terms of the investment in OAO VNIPIneft, which specializes in oil refining, gas processing, petrochemicals and chemicals, were not disclosed.

The deal demonstrates a more aggressive approach to mergers and acquisitions, said Genuity Capital Markets analyst Maxim Sytchev. The timing is opportune, he added, because chemical and petroleum sectors are weak this year and relatively affordable due to the economic downturn.

Expect more acquisitions in this space, he wrote in a research note that estimated SNC's share of annual revenue from the Russian firm at about C$43 million ($36 million).

We believe this is only a beginning of SNC-Lavalin's M&A program in the oil and gas sector as the company strives to establish a larger footprint in Northern Africa, Russia, Middle East and Venezuela.

Moscow-based OAO VNIPIneft, with about 900 employees, has designed more than 40 refineries and industrial projects in Russia, Europe and the Middle East.

Jean Beaudoin, the head of SNC's chemicals and petroleum unit, said the Montreal-based engineering and construction company has been operating in Russia for more than 30 years and considers it a key market.

In June SNC signed an agreement to manage the construction and maintenance of roads and railways for the 2014 Winter Olympics in Sochi, Russia.

SNC has worked with OAO VNIPIneft for several years, Sytchev wrote, and is unlikely to buy the entire company because the Russian government is also a shareholder.

SNC-Lavalin needs to have a partner in Russia if it wants to carry out work for quasi-state oil and gas companies, he wrote.

Shares in SNC lost 73 Canadian cents, or 1.4 percent, to close at C$49.26 on the Toronto Stock Exchange on Friday.

($1=$1.10 Canadian)

(Reporting by Susan Taylor; editing by Peter Galloway)