The leaders of South Korea and Saudi Arabia agreed Thursday to boost ties in key sectors such as energy and defence, with the oil-rich kingdom signing a slew of deals including a $6.7 billion petrochemical agreement.

President Yoon Suk-yeol met with Saudi Arabia's Crown Prince Mohammed bin Salman in the South Korean capital Thursday, with the pair announcing a plan to transform bilateral ties into a "strategic partnership".

Bin Salman, the kingdom's 37-year-old de facto ruler, often referred to as MBS, arrived in Seoul late Wednesday after attending the Group of 20 summit in Bali, Indonesia.

He is on a multi-stop Asian tour, in a likely bid to shore up the Gulf nation's ties with its biggest energy market.

The trip comes as Riyadh feuds with Washington over the OPEC+ oil cartel's October decision to cut production by two million barrels per day.

Yoon and bin Salman agreed to elevate ties into a "future oriented strategic partnership," Yoon's office said in a statement.

The South Korean president wants to see local companies join key Saudi projects such as the NEOM smart city project, and boost cooperation in the defence and energy sectors.

Bin Salman "especially expressed his wish for a significant increase in cooperation in energy, defence and construction industries," Yoon's office said.

During the visit, the two governments and companies from both countriesincluding some of Seoul's top conglomeratessigned about 20 deals in areas from agriculture to railways.

Among the agreements was Saudi investment for South Korean refiner S-OIL's Shaheen project, which would build petrochemical production facilities in South Korea worth $6.7 billion, Yoon's office said.

Bin Salman, who was officially made Prime Minister in September, has shaken up the ultraconservative oil titan with economic, social and religious reforms since his meteoric rise to power.

He gained global notoriety in connection with the 2018 killing of dissident Saudi journalist Jamal Khashoggi in the kingdom's Istanbul consulate.

Last year, US President Joe Biden declassified an intelligence report that found Prince Mohammed had approved the operation against Khashoggi, an assertion Saudi authorities deny.