Russian President Vladimir Putin has hosted Saudi King Salman for talks at the Kremlin, in the first official visit to Russia by a reigning Saudi monarch.
Putin hailed the visit as a "landmark" event as he welcomed King Salman at the Kremlin on October 5.
"I'm sure your visit will boost the ties between our countries," he added.
"We aim to strengthen our relations in the interests of peace and security, in the interests of developing the world economy," the Saudi monarch responded.
He also said that that Riyadh is "eager to continue the positive cooperation between our nations in the world oil market."
Relations between the world’s two largest oil-export nations have often been strained.
During the Cold War, the Saudis helped arm Afghan rebels fighting against the Soviet occupation.
More recently, the two countries have had differences over Iran, Saudi Arabia’s main rival in the Middle East, and the war in Syria.
Riyadh supports U.S.-backed rebels fighting against Syrian President Bashar al-Assad's government, while Russian troops and Iranian militias have backed Assad in the country’s six-year civil war.
Despite regional disagreements, Russia and Saudi Arabia found common ground on energy policy in November, when they worked together to secure a deal between OPEC and other oil producers to cut production in an effort to drive up oil prices.
Briefing the media on the talks between Putin and the 81-year-old king, the Russian and Saudi foreign ministers focused on the common ground between the two countries.
Russian Foreign Minister Sergei Lavrov said the two leaders had a "friendly and substantial discussion based on a desire by Moscow and Riyadh to consistently grow mutually beneficial partnerships in all spheres."
He also said the two agreed on the importance of fighting terror and of finding peaceful solutions to conflicts in the Middle East.
Speaking alongside Lavrov, Saudi Foreign Minister Adel al-Jubeir said that Moscow and Riyadh agreed on the need to preserve Syria's territorial integrity.
"We believe that new horizons have opened up for the development of our relations that we could not previously have imagined," he also said.
Lavrov also said the two sides “signed a whole package of intergovernmental and interdepartmental agreements, and large-scale commercial contracts."
The deals included preliminary agreements on the purchase of S-400 air-defense systems, Kornet antitank guided-missile systems, and multiple rocket launchers, according the state-owned Saudi Arabian Military Industries.
It did not specify the potential value of the deals but said the procurement was "based on the assurance of the Russian party to transfer the technology and localize the manufacturing and sustainment of these armament systems in the Kingdom."
Russian and Saudi officials also signed an agreement on the creation of a $1 billion joint investment fund, Reuters reported.
Another memorandum of understanding was signed under which Sibur, Russia's largest producer of petrochemicals, would explore cooperation with Saudi Arabia.