Indonesia's central bank believes the rupiah's depreciation is due to a strong U.S. dollar and higher foreign exchange (FX) demand from domestic firms and banks, a Bank Indonesia (BI) official said on Wednesday.

Edi Susianto, its head of monetary management, told Reuters BI would continue to be in the market to ensure the balance of FX supply and demand.

"The current situation of FX supply and demand is still under control," he said.

The rupiah weakened 0.37% to 15,844 against the U.S. dollar at 0544 GMT on Wednesday, its lowest since Nov. 2. (Reporting by Stefanno Sulaiman; Editing by Kim Coghill, Martin Petty)