SYDNEY - Australia's Offshore Alliance union said on Saturday workers had begun a 24-hour strike at Chevron's liquefied natural gas (LNG) plants in western Australia, as part of a ramp-up in industrial action that could see strikes extended until mid-October.

The full strike comes after workers on Thursday escalated what had been six days of limited action. Until the end of September, members of Offshore Alliance, a coalition of two unions, can now strike for up to 24 hours each day and refuse tasks such as loading LNG tankers.

The company's Gorgon and Wheatstone Australian LNG facilities account for over 5% of global supply.

"Chevron’s 3 West Coast facilities are descending into chaos as Offshore Alliance members lock all 3 Chevron facilities down for the next 24-hours," the union said in a Facebook post.

An union representative, who declined to be identified, said the strike would run until 8am WST on Sunday (0000 GMT). Meetings would be held twice daily to decide on further strikes.

The representative also said the unions would file notice with Chevron that they intend to extend industrial action for a further two weeks to mid-October.

Chevron has asked Australia's industrial tribunal to intervene in the dispute and cancel the strikes. The tribunal will hold a hearing on Friday and a decision is expected shortly after.

A Chevron spokesperson declined to comment on the union's Facebook post. The company has previously said it would not provide ongoing comments on the strikes but would take steps to maintain operations in the event of disruptions.

An outage at the Wheatstone facility on Thursday cut LNG production by about a quarter. A spokesperson said on Saturday that restart activities were continuing. It is not clear if the strikes are disrupting the resumption of full production.

Unions have said they will vary strikes according to "industrial strategy", targeting LNG exports in particular.

Analysts say the strikes pose little risk to global LNG supplies as they are likely to be temporary and key gas buyers have plenty of inventory ahead of the northern winter.

(Reporting by Sam McKeith and Lewis Jackson in Sydney; Editing by Sandra Maler and Kim Coghill)