NEW DELHI (Reuters) - India's industrial output in January grew at a weaker-than-expected rate of 3.8% year-on-year, on the back of slowdown in manufacturing and mining activity, government data showed on Tuesday.

Economists polled by Reuters had estimated growth of 4.1% in industrial output in January. The industrial output for December has been revised upwards to 4.2% from 3.8%.

Manufacturing output in January rose 3.2% year-on-year, slower than 4.5% in the same month in the previous year.

Electricity generation in January was up 5.6%, against 12.7% growth in the corresponding month a year earlier. Mining activity increased by 5.9%, compared with a 9% rise in the same month a year earlier, the data showed.

Industrial output in the first 10 months of the fiscal year which started in April was up 5.9%, against 5.5% in the same period a year earlier.

(This story has been corrected to fix the revised industrial output number for December by economists to 4.2%, not 3.8%, in paragraph 2)

(Reporting by Sarita Chaganti Singh; Editing by Alex Richardson)