Libya had been in talks with Russia for several days
Russia is to supply Libya with small-arms and other weapons to the value of $1.8bn (£1.1bn, 1.3bn euros), Prime Minister Vladimir Putin has announced.
The contract is worth nearly a quarter of the Russian state arms exporter's entire sales last year, which were put at $7.4bn.
Mr Putin said the deal had been signed on Friday during a visit by the Libyan defence minister.
There was no immediate word from the Libyan side on the deal.
Abu Bakr Yunis Jaber, Libya's defence minister, has been in Moscow for several days, meeting defence officials.
Mr Putin gave no details of the arms covered by the contract. Russian media speculated earlier that it might include fighter planes.
"Yesterday a contract worth 1.3bn euros was signed," Mr Putin announced at a meeting near Moscow with the director of the Russian small-arms manufacturer Izhmash, which makes the Kalashnikov assault rifle.
"These are not just small-arms."
Mr Putin gave no further details. However, according to a military diplomatic source quoted earlier by Russian news agencies, the deal included fighter aircraft, tanks and a sophisticated air defence system.
Rosoboronexport, Russia's state-owned arms export monopoly, announced on Thursday that its 2009 sales had seen a 10% increase on the previous year.
Customers included India, Algeria, China, Venezuela, Malaysia and Syria, with air force weaponry making up 50% of sales.