BENGALURU - A bout of late selling in automakers and banks knocked India's blue-chip stock indexes off four-week highs and into negative territory on Friday, although strength in information technology shares and Reliance Industries helped limit the decline.

The NSE Nifty 50 index closed 0.26% lower at 16,584.3, while the S&P BSE Sensex slipped 0.09% to 55,769.23. The indexes still clocked their third straight week of advances with gains of around 1.5% each.

"There is huge volatility in key economic variables and commodity prices, especially crude, which is keeping investors on edge," said Saurabh Jain, assistant vice president research, SMC Global Securities. "Inflation is still the major concern."

Earlier in the session, both the Nifty and the Sensex had risen as much as 1% as Reliance Industries hovered just shy of record highs and IT stocks tried to stage a recovery after eight straight weeks of losses.

The Nifty IT index gave up some gains to close 0.37% higher and notched a weekly rise of around 4.4%. The index has dropped 22.7% so far this year amid losses in global peers on concerns over valuations and attrition.

Shares of Reliance Industries - India's most valuable company - climbed 2% and were among the biggest boosts to the indexes.

The Nifty Auto index led losses among sub-indexes with a 1.8% drop. India's top carmaker Maruti Suzuki fell 2.8%. The Nifty PSU Bank index, which tracks state-run lenders, slipped 1.4%.

Shares of UltraTech Cement slid 5.5% after the company said it would spend $1.66 billion to boost capacity as it looks to stave off competition from the sector's newest entrant Adani Group.

Grasim Industries - UltraTech Cement's parent company - fell 6.5%, while rivals Shree Cement, ACC and Ambuja Cements also declined.

Meanwhile, specialty chemicals firm Aether Industries closed 20.6% higher in its market debut after its $104 million initial public offering received a strong investor response.

(Reporting by Chris Thomas in Bengaluru; Editing by Sherry Jacob-Phillips and Aditya Soni)