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* Sharpest rise this year; traders say stocks built before rains
* Rupee slump limits gains to importers from global coal price fall
* Half-yearly total coal imports jump 28.3 pct y/y in 2013
By Malini Menon
NEW DELHI, Aug 21 (Reuters) - India's thermal coal imports rose in June at their fastest pace in 2013 and jumped by more than half from a year ago as traders and power utilities stocked up to get through the monsoon season, provisional data from government sources showed.
The surge in shipments at the world's fourth-largest coal importer is bad news for India which is restricting imports of commodities such as gold and silver in an attempt to halt a three-month slump in its currency. The rupee fell to an all-time low of 64.13 against the U.S. dollar on Tuesday.
The decline in the currency is making the imports costlier even as international coal prices are weakening and has raised the urgency for domestic producers such as Coal India Ltd to lift their flagging output.
Thermal coal shipments to India were 12.02 million tonnes in June, up 52.5 percent from 7.88 million tonnes imported in the same month of last year, data obtained by Reuters showed.
Local supplies typically fall during the June-September monsoon season due to lower production, prompting coal traders and consumers to stock up before restrictions kick in at several ports due to squally weather conditions.
Energy-hungry India relies on coal to fuel more than half of its power generation, but domestic production has not kept up with capacity additions in the power sector, leading to power cuts that crimp growth and also result in costlier imports.
Last year, 670 million people in the northern, eastern and northwestern parts of the country had no power for two days, the biggest outage in the world, as a few states drew excess power from the national grid causing it to snap.
During the first half of the calendar year, India's overall overseas coal purchases, which include coke and briquettes, rose 28.3 percent from a year earlier to 75.73 million tonnes, the data showed.
The numbers could only go up as ports, where documentation is done manually, send their figures to the government with a considerable time lag, one of the sources said.
Total coal imports this fiscal year to March 31, 2014 could hit a record 165 million tonnes from 137.56 million tonnes in 2012/13, according to the government.
India does not release coal import data on a regular basis. It places no restrictions on the imports of the commodity, which are shipped in by traders and mainly power utilities.
India's total coal imports also rose in June at their fastest pace this year - up 27.19 percent to 15.46 million tonnes - the data showed.
Prices for Australian coal, the benchmark for Asia, have fallen about 38 percent since hitting a record high of $130 per tonne in 2011. They are down 15.48 percent since January.
The cost of June's total import volumes rose 28.1 percent from a year ago, pushed up by a falling rupee, to 49 billion rupees ($770.99 million).
Coal ranks seventh in India's import bill of around $448 billion annually according to the commerce and industry ministry, after crude oil, gold and edible oils, among others.
Coking coal imports, however, dropped nearly a quarter in June to 2.75 million tonnes, its fifth straight monthly fall, on modest demand for the steelmaking ingredient, the data showed.
Indonesia shipped out 9.4 million tonnes, remaining as the No. 1 coal exporter to India and accounting for 61.1 percent of the total shipments in June. Australia grabbed a 16.8 percent share, while South Africa's share was 13.9 percent. ($1 = 63.5550 Indian rupees) (Editing by Muralikumar Anantharaman)