Reuters Market Eye - The BSE Sensex is down 0.27 percent, heading for a seventh day of fall, while the 50-share Nifty is 0.25 percent lower, near its lowest level since March 22.
Both indexes are close to breaking their 200-day moving averages. The BSE index is a shade above its lowest intraday level since November 27, 2012.
Dealers say the indexes are falling due to concerns other allies could withdraw support from the ruling coalition, after the withdrawal of the Dravida Munnetra Kazhagam (DMK) party last week.
Blue chips such as ICICI Bank Ltd falls 1.2 percent, while Infosys Ltd drops 0.4 percent and Bharti Airtel Ltd is down 1.6 percent.
Weak Indian shares contrast with the rally in global shares after Cyprus clinched a tough last-ditch bailout deal.
(Reporting by Abhishek Vishnoi)