Jakarta – Pertamina may have caused the further depreciation of the rupiah against the US dollar, as it reached Rp9,500 on Wednesday, an official from Bank Indonesia said.

"Today's further weakening of the rupiah [occurred] as state oil/gas company Pertamina had also bought the greenback amounting to US$100 million [Rp 945.5 billion], and we still do not know for what purpose," an official at Bank Indonesia (the country's central bank), who refused to be named, said on Wednesday.

The source said Bank Indonesia had already asked Pertamina about the purpose of the dollar purchase, but the state oil/gas company refused to give an explanation.

Pertamina has often made foreign currency purchases at a time when the rupiah has started to weaken, and these purchases have caused increased pressure on the Indonesian currency. "If there was no such an action [the buying of dollars] by Pertamina, the rupiah would not be so weak as it is today," he said.

The source also called on the government to better coordinate with Pertamina to prevent the rupiah from further weakening.

Bank Indonesia has often asked the government to warn Pertamina to refrain from dollar purchases, especially when the rupiah is rather weak, but Pertamina has not taken notice of the warning.