Mikhail Dmitriyev, head of the Federal Service for Military-Technical Cooperation, said Russia would supply Syria with MiG-29 fighters, truck-mounted Pantsir short-range surface-to-air missiles and anti-aircraft artillery systems.
He said Russia would also supply Damascus with anti-tank weapons but did not specify their type.
Syria's regional foe Israel reacted angrily to the deal but called into question the solvency of Damascus.
"Syria at the present time cannot afford to pay for this sophisticated weaponry, indeed, it has hardly enough money to buy food for its citizens. One can only wonder what is the real reason behind this dubious deal," said an Israeli government official in Jerusalem who declined to be named.
Israel's close ally the United States imposed sanctions on Syria for its support of militant groups and corruption.
Earlier this week, Russian President Dmitry Medvedev visited Syria — the first visit to Damascus by a Moscow ruler since the 1917 Bolshevik revolution — and oversaw talks on Russia's possible assistance in building a nuclear power plant in Syria.
While in Syria, Medvedev unnerved Israel by paying a visit to Khaled Meshaal, the exiled leader of the Palestinian Islamist group Hamas.
"Russia's haste to win this contract has seen it even willing to meet with notorious Hamas leaders in Syria," the anonymous Israeli official said.
Israel's Foreign Ministry said it was "deeply disappointed" that Medvedev met the leader of Hamas, which it said was "a terror organization in every way."
