FACTBOX-Armenia's economy

(Reuters) - Armenians voted on Tuesday in a presidential election that Prime Minister Serzh Sarksyan is expected to win.

The ex-Soviet state has enjoyed strong economic performance in the past few years, with gross domestic product growing in 2007 by 13.7 percent.

But credit rating agency Moody's Investors Service said in November that Armenia's economy could be vulnerable to an international slowdown and a cooling of its booming construction sector.

Russian firms control a significant chunk of the economy. Below are facts about the biggest foreign investors in Armenia:

* Armenia has given the Russian state railway monopoly a 30-year contract to run the national railway network for 1.7 billion drams (2.8 million pounds).

* Russian mobile operator Vimpelcom has become sole owner of Armenia's mobile and telecom operator Armentel after paying $488 million.

* Russia's top cellular operator Mobile TeleSystems (MTS) acquired 80 percent in Armenia's K-Telecom, which operates under the Vivacell brand, for 310 million euros (234 million pounds).

* An Armenian foil plant is controlled by Russia's RUSAL, the world's third-largest aluminium producer.

* Iran and Armenia have built a new $200 million (102 millino pound) gas pipeline to transport Iranian gas to Armenia in exchange for electricity supplies. Russian-Armenian company ArmRosGazprom -- in which Russian gas giant Gazprom owns 57.6 percent, the Armenian government holds 34.7 percent and Russian gas producer Itera owns 7.7 percent -- is to operate the new pipeline.