The rupee had slumped to a record low of 59.9850 rupee to the dollar on Thursday, as the country's record high current account deficit is exacerbating its vulnerability in an emerging market rout.
The intervention was spotted when the rupee hit 59.90 to the dollar or below
Overall Indian companies issued guarantees worth $1.21 billion, extended loans worth $291 million and pumped in equities worth $319 million.
Heightened volatility makes the debt rollovers difficult.
The RBI said it had not found initial evidence of money laundering against the three banks.
Import duty on gold is already hiked by a third to 8 per cent.
RBI will auction Rs 1,000 crore worth of these bonds next Tuesday.
High current account deficit is leading to the rupee weakening.
Monetary policy committee had recommended no change in the key rate.
The central bank, however, would prefer money supply in deficit mode.
The majority view remains for the central bank to leave the cash reserve ratio unchanged at 4 per cent.
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Keeping that much money out of the banking system has created a liquidity deficit that has forced banks to borrow as much as RS 1.6 trillion from the central bank to meet daily funding needs.
Current account deficit could ease to around 3 per cent in the current fiscal year from prior estimates of about 4 per cent due to sharp drop in global commodity prices.
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It feels govt may find it challenging to meet the revenue projections.
Domestic and external environment still remain "challenging".
Majority of the experts expect a 25 basis point reduction.
They shied away due to concerns over asset quality and a rise in NPAs.
Rates India 'BBB-' with a negative outlook.