SEOUL, Oct 8 (Reuters) - South Korea's central bank said on Thursday it has agreed to renew a currency swap agreement with China, adding details including the extension period and size will be disclosed later.

"The Bank of Korea reached a working-level agreement with the People's Bank of China to extend the currency swap deal, and will announce details as soon as necessary procedures are completed," it said.

The existing $56 billion currency swap deal was set to expire on Saturday. (Reporting by Joori Roh; Editing by Kim Coghill)