Under the agreements, Saudi Arabia is set to buy S-400 air defence systems, Kornet anti-tank guided missile systems and multiple rocket launchers.
King Salman said Saudi-Russian relations were characterized by similar views on many regional and global problems.
The pact between the OPEC, Russia and other producers on cutting output by about 1.8 million barrels per day (bpd) is now due to expire in March.
Russian analysts say that King Salman is seeking to diversify Saudi alliances because of uncertainty over Donald Trump's Middle East polices.
"The leaders of other countries welcomed the creation of yet another commission, the commission on defense industry cooperation, which should hold its first meeting before the end of year", Lavrov said after the talks of the Russian president with the Saudi king.
But prices are still half their mid-2014 levels.
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"The two have been coordinating their efforts to cap oil outputs and therefore boost the price of energy, but of course there is the changing political structure of the Middle East too", he said.
Russian Federation and Saudi Arabia, among other agreements expected to be signed during this bilateral summit, will create a billion-dollar investment fund for different energy projects.
Putin said the agreement to cut oil production previous year between OPEC and non-OPEC countries could be extended beyond March 2018 but an announcement was unlikely before the next OPEC meeting in Vienna at the end of November.
The 81-year-old Saudi monarch's three-day visit got off to an awkward start on Wednesday evening after landing at Moscow's Vnukovo-2 airport when the escalator he uses to descend from his plane malfunctioned.
The deal was reportedly reached on the sidelines of the visit by Saudi King Salman bin Abdulaziz Al Saud to Moscow.
The king is also set to met Prime Minister Dmitry Medvedev on Friday before leaving Russian Federation on Saturday.
According to the Russian minister, the Russia-Saudi Arabia intergovernmental commission will meet in late October in Riyadh for the fifth time.
He also mentioned that Russian firms have been discussing possible future deals with energy giant Saudi Aramco, such as the provision of drilling services in Saudi Arabia and in crude trading.