Shiite powerhouse Iran and Sunni-majority Saudi Arabia are regional foes.
The most important economic deal was signed by Russian state wealth fund RDIF and Saudi Arabia's Public Investment Fund and Mubadala.
While they are partners on the oil market, on the foreign policy front, Moscow and Riyadh land on opposite sides of the Syrian conflict, with Russian Federation supporting the regime of Bashar al-Assad while Saudi Arabia supports his opposition.
Saudi Arabia has signed preliminary agreements to buy S-400 air defence systems from Russian Federation, officials said, on the sidelines of King Salman's "landmark" visit to Moscow. King Salman paid back the compliments by saying Russian Federation was a "friendly country". "As far as bilateral ties with the United States are concerned, their current level can not be satisfying", Putin said at the Kremlin after he received diplomatic credentials from Huntsman.
Russia-Saudi defense industry cooperation is not directed against third countries, Kremlin spokesman Dmitry Peskov said Friday. "The political will of Moscow and Riyadh for deeper cooperation on the widest range of issues is clear".
In July 2015, when the friendship between the then Crown Prince Salman and President Putin blossomed, Riyadh pumped $10 billion of investments into the Russian economy.
On a historic visit to Moscow on Thursday, Saudi Arabia's King Salman criticized arch-foe Iran, a Russian ally, voiced support for a two-state solution to the Israeli-Palestinian conflict and signed multi-billion dollar defense and energy deals with Russian officials.
Saudi Arabia and Russian Federation have a joint interest in diversifying their economies away from oil as the price is still trading well below historic highs.
Saudi Arabia is the most prominent oil-producing member of OPEC, making it the organization's de facto leader.
Novak said the two countries' business circles maintain intensive dialogue, and he pointed out that the Saudi delegation to Moscow included 85 chief executives of major Saudi companies. This means Moscow is allied with Iran, whose growing influence in the region is the primary source of concern for Saudi Arabia.