* Kansai to buy 500,000 tpa LNG for 15 years from 2013
* Deal is in addition to existing contract worth 290,000 tpa
* Qatargas supplying Japan with 11 mln T extra LNG in short term (Adds details)
TOKYO, Sept 26 (Reuters) - Japanese utility Kansai Electric Power Co said it had signed a contract with the world's top LNG producer Qatargas on Wednesday to buy 500,000 tonnes per year (tpa) of liquefied natural gas (LNG) for 15 years from January 2013.
The deal, which is in addition to an existing contract for 290,000 tpa for 23 years from 1999 to 2021, was signed with Qatargas 3, Japan's second-biggest utility said in a statement.
The move comes as the company has been increasing spot LNG purchases from Qatar to fill the void of nuclear power it had lost following the massive March 2011 earthquake and tsunami that devastated Tokyo Electric Power Co's Fukushima Daiichi nuclear plant, a company spokesman said.
Kansai bought 1.79 million tonnes of Qatari LNG in the year ended in March, accounting for 24 percent of Kansai's total LNG imports, the spokesman said.
Qatargas said on Sept. 12 that it would supply Japan with 11 million tonnes more of LNG in the short term, in addition to 9 million tonnes announced last autumn.
Japanese utilities have been ramping up gas-fired power generation as all but two of Japan's 50 nuclear reactors remain offline due to public concerns about atomic safety.
The deal also came after Tokyo Electric said in June that it has signed a new contract with Qatargas to purchase 1 million tonnes per year of LNG from August. (Reporting by Osamu Tsukimori; Editing by Michael Watson and Chris Gallagher)