"What's happening in the Gulf is definitely a concern," Amin Nasser, president and chief executive of Saudi Arabia's state oil giant, told Reuters in an interview.

"At the same time we went through a number of crises in the past ... we've always met our customer commitments and we do have flexibility and the system availability in terms of available additional spare capacity."

Recent tanker attacks in the Gulf have raised fears about safety of one of the world's key shipping routes and pushed up oil prices.

Nasser, who is in Seoul ahead of a visit by Saudi Crown Prince Mohammed bin Salman, said Aramco has no plan to increase its current maximum output capacity of 12 million barrels per day (bpd), given sizeable spare capacity.

"If you look at our production, it is hovering around 10 million barrels per day so we do have additional spare capacity," he said.

The oil giant is aiming to become a major global gas player, and has been developing its own gas resources as well as eyeing gas assets in the United States, Russia, Australia and Africa.

Nasser said Aramco is in talks to buy a stake in Russian gas company Novatek's Arctic LNG-2 project, while exploring other investment opportunities in gas.

He confirmed the company is also in discussions about buying a stake in India's Reliance Industries and in talks with other Asian companies about investments.

"We will continue to explore opportunities in different markets and different companies, and these things take time," he said.

Nasser said the company, South Korea's top oil supplier, was looking to increase its crude oil supplies to the country where it has partnerships and investments with South Korean refiners.

Saudi Aramco supplies between 800,000 barrels per day (bpd) and 900,000 bpd to South Korea, the world's fifth-largest crude importer.