UPDATE 1-Hyundai Motors shares slump after production suspended in China

* China factories suspended over past week - Hyundai

* Shares fall to lowest since April 20

* S.Korean firms facing Chinese backlash (Adds company comment, background)

SEOUL, Aug 30 (Reuters) - Shares of Hyundai Motor skidded to their lowest level in more than four months on Wednesday, after the South Korean automaker said it had suspended production at its four Chinese factories since last week due to supply disruption.

Hyundai Motor shares fell as much as 3.8 percent to their lowest since April 20, after Hyundai Motor said that a supplier had refused to supply parts to Hyundai Motor.

The automaker's Chinese joint venture was unable to pay the supplier, a Hyundai spokeswoman said, without providing the reasons.

Hyundai has a joint venture with China's BAIC Motor Corp Ltd in China and is grappling with a sales slump linked to diplomatic tensions between Seoul and Beijing. It was scheduled to start operations at a fifth factory in China this month.

South Korean firms are weathering a Chinese backlash over Seoul's decision to deploy a U.S. missile defense system to counter threats from nuclear-armed North Korea. China says the system poses a threat to its national security.

Hyundai Motor's sales from its Chinese factories fell 64 percent to 105,000 vehicles in April-June alone. (Reporting by Hyunjoo Jin; Editing by Stephen Coates)