Cleary Gottlieb Steen & Hamilton has advised Malaysian state-owned oil and gas company Petroliam Nasional Bhd. on a $5 billion debt issue, the largest so far this year in Asia.

The company, also known as Petronas, issued a mix of Islamic and conventional bonds as part of a newly established $15 billion medium-term note program. The proceeds will be used to shore up Petronas’ balance sheet following a significant drop in oil prices since last summer.