The landmark $30 million deal was pulled together by Argentina's Defense Ministry and Russia's Rosoboronexport government arms export agency. The ceremonious signing highlighted a visit by Russian President Dmitry Medvedev to Argentina -- the first by a Russian leader since Moscow established diplomatic relations with Buenos Aires 125 years ago.
It is the Russian leader's second trip to Latin America since he became president in 2008. In November that year, he made a four-nation trip to Brazil, Cuba, Peru and Venezuela.
With the deal, Argentina joins seven other Latin American countries -- Bolivia, Brazil, Colombia, Mexico, Peru, Uruguay and Venezuela -- that have increasingly turned to Russia for weapons.
The deal also comes amid designs by Russia and Argentina to bolster relations in nuclear power development and share use of the Russian Global Navigation Satellite System.
Argentina has two nuclear power plants in service. A third is under construction, while Argentine President Cristina Fernandez de Kirchner has said a fourth was under consideration but there was no indication of the project's estimated cost.
Argentina generates about 20 percent of its electricity by using Russian-made equipment, Russian Economy Ministry says.
Argentina abandoned a nuclear weapons program in the 1990s. Kirchner stressed there was no intention of returning to militarization and that the deal opted to help Buenos Aires develop its civilian nuclear energy program.
"The world has changed," Kirchner said. "We are no longer a backyard of another country."
The Russian company, Rosatom Corporation, is Moscow's state-owned holding company that will be involved in the design. It is on schedule to complete Iran's first nuclear reactor in the southern city of Bushehr later this year. The company insists the reactor doesn't threaten nuclear non-proliferation pacts.
"Russia is back in Latin America," Medvedev said after the signing of the accords, adding that his country wanted to establish "tight cooperation" with the region.
Earlier this month, Rosoboronexport delivered the first three of a dozen Mi-35 combat helicopters to Brazil, following an order placed in 2008. An additional three such helicopters are to be delivered to the Brazilian air force this year.
The Russian company signed the purported $1.5 billion contract, winning over rival EADS's Tiger and the Italo-Turkish production of the AW-TAI A129 Mongoose.
Related agreements were also signed between Argentina and Russia for cooperation in the field of railway transportation.