BENGALURU, Dec 18 (Reuters) - India's Nifty 50 and Sensex opened lower on Monday after rallying to record highs for most of this month, while other Asian markets were subdued ahead of Japan's monetary policy decision on Tuesday.

The benchmark NSE Nifty 50 index lost 0.35% to 21,381.30 points, while the S&P BSE Sensex shed 0.45% to 71,168.57, as of 9:16 a.m. IST. (Reporting by Bharath Rajeswaran in Bengaluru; Editing by Varun H K)