By Florence Tan and Trixie Yap

SINGAPORE, Aug 23 (Reuters) - Malaysian state energy firm Petronas is in talks with sellers to buy Middle East crude loading in October for its joint-venture refinery with Saudi Aramco as the plant ramps up output, trade sources said on Friday.

Petronas and Aramco 2222.SE have equal shares in the Pengerang Refining Company (Prefchem), also known as RAPID, which can process 300,000 barrels per day (bpd) of crude oil at its complex at Pengerang in Malaysia's southern state of Johor.

The refinery is increasing its crude processing rate this month, up from about 50% in July, some of the sources said.

Refining runs have been curtailed earlier due to maintenance at other refining units including the atmospheric residue desulphurisation unit, they added.

A rise in output from the RAPID refinery will increase refined products supply in the region and weigh on refining margins, traders said.

Prefchem did not respond to a request for comment.

The RAPID refinery is set to boost its crude imports this month to about 202,000 barrels per day, the highest since June 2023, estimates from analytics firm Kpler showed.

It was not immediately clear how many October-loading cargoes Petronas will buy for PrefChem.

The RAPID refinery typically processes Oman and Qatari al-Shaheen crude in addition to long-term Saudi crude supply from Aramco.

(Reporting by Florence Tan and Trixie Yap; Editing by Clarence Fernandez)

((Florence.Tan@thomsonreuters.com; Reuters Messaging: florence.tan.thomsonreuters.com@reuters.net))