At 10:15 am, the BSE S&P Sensex was down by 179 points to 36,945 while the Nifty 50 edged lower by 42 points to 10,962.
At the National Stock Exchange, sectoral indices were mixed with Nifty auto down by 0.7 per cent. Nifty bank, financial service, IT, media and pharma too were in the red while FMCG, metal and realty inched up with small margins.
Auto majors Hero MotoCorp and Tata Motors were down by 1.3 per cent and 0.9 per cent respectively. IT majors HCL Technologies and Tech Mahindra also lost by 1.7 per cent and 1.5 per cent.
Indiabulls Housing Finance, Axis Bank, Bharti Infratel, Bharti Airtel, Bharat Petroleum Corporation and UltraTech Cement too were in the red.
However, those which showed marginal gains were Yes Bank, Vedanta, Titan, Asian Paints and Hindalco.
Meanwhile, investors in Asian markets remained broadly on the sidelines ahead of an expected interest rate cut from the US Federal Reserve and the next round of US-China trade talks later this week.
MSCI's broadest index of Asia Pacific shares outside Japan was down by 0.6 per cent while Chinese shares fell by 0.85 per cent.
The investor sentiment took a hit following Saturday's attack on Saudi oil facilities which halved the kingdom's oil output, creating the biggest disruption to global oil supplies in absolute terms since 1979, said reports quoting data from the International Energy Agency.