The total reserves had risen $2.44 billion to $294.47 billion in the previous reporting week.
Foreign currency assets, a major component of the forex reserves, were down by $485.6 million to $261.03 billion for the week ended September 21, RBI's weekly statistical supplement showed.
Foreign currency assets expressed in US dollar terms include the effect of appreciation or depreciation of the non-US currencies, such as the euro, pound and yen, held in the reserves, the apex bank said.
The gold reserves remained unchanged at $26.24 billion during the week, the apex bank said.
For the week under review, the special drawing rights (SDRs) were down by $11.2 million to $4.460 billion, while the country's reserve position with the IMF was also down $5.6 million to $2.243 billion, the apex bank data showed.