NEW DELHI—India’s consumer inflation reached its lowest level in nearly three years in September on declining food and fuel prices, generating hope that it could ease even more and allow policy makers to focus on boosting economic growth.

The consumer-price index rose 6.46% from a year earlier, according to government data issued Monday. The reading was much lower than August’s 7.73% and the median forecast of 7.1% by economists surveyed by The Wall Street Journal.

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