The Sensex at the Bombay Stock Exchange plunged 328 points or 1.7 percent, to 18,670, in afternoon deals, a short while ago, on heavy selling in banking and other interest-rate-sensitive stocks, after the Reserve Bank today hiked key policy rates sharply to tame inflation. Earlier in the morning, the Sensex had opened 97 points, or 0.5 percent in the red, at 18,901. The benchmark Sensex has already lost over 600 points in the last six trading sessions. Stock markets in China, South Korea, Indonesia, Singapore and Taiwan were down by between 0.1 percent and 1.3 percent.