UPDATE 1-Saudi crown prince seeks S.Korea's help to bolster defences after attacks

(Adds details, background)

SEOUL, Sept 18 (Reuters) - Saudi Arabia’s crown prince Mohammed bin Salman asked South Korea on Wednesday to help strengthen the country’s air defence system after attacks on two oil plants, Seoul’s presidential office said.

The request was made during a phone call with South Korean President Moon Jae-in, who expressed condolences over the damage from the attacks and support for a global fight against terrorism, Moon’s office said.

Last weekend’s attacks on the Saudi crude facilities initially halved the country’s crude production, sending oil prices to four-month highs and prompting South Korea to consider releasing oil reserves.

South Korea is the world’s fifth-largest crude oil importer and sources about 30% of its needs from Saudi Arabia.

Moon offered to assist reconstruction efforts, and the crown prince said two-thirds of the facilities have been restored and that production will be put back on track “100%” within 10 days, Moon’s office said.

“He requested help to establish an anti-aircraft defence system to prevent future attacks,” it said in a statement. (Reporting by Hyonhee Shin in Seoul; Additional reporting by Hesham Elsaba in Dubai; Editing by Kim Coghill)