MOSCOW (AP) — Russian President Vladimir Putin and Saudi Arabia's King Salman on Thursday opened talks in the first official visit of a Saudi monarch to Russia that's expected to focus on the oil market and the war in Syria.

At the Kremlin's opulent St. Andrew's Hall, Putin in televised remarks hailed the king's visit as a "landmark" event. King Salman in his reply called Russia a "friendly nation" and said his country is committed to strengthen ties "in the interests of peace and security."

Relations between the two countries have often been strained. During Cold War times, the Saudis helped arm Afghan rebels fighting against the Soviet invasion.

More recently, tensions were high over the war in Syria, in which Russia has staunchly backed Syrian President Bashar Assad while Saudi Arabia has supported his foes.

However, relations have begun to improve in recent years and King Salman's heir, Crown Prince Mohammed bin Salman, has held several meetings with Putin.

The kingdom, much like Russia, has been hit by the fall in oil prices since mid-2014. Despite regional disagreements, the two countries found common ground on energy policy in November when they led a deal between OPEC and non-OPEC states to cut production in a bid to shore up crude prices. So far that deal is holding.

The two sides are expected to announce large investments and joint ventures to further cement relations. Trade volume between the two countries reached $2.8 billion last year, according to official Saudi press.