* Fin Min Noda says communicating with authorities abroad (Adds finance minister Noda, market comments)

TOKYO, Sept 15 (Reuters) - Japan intervened in the currencymarket on Wednesday for the first time in six years, selling yento stem a rise in the currency that is threatening a fragileeconomic recovery.

Finance Minister Yoshihiko Noda confirmed the intervention ina news conference, saying Tokyo was also communicating withauthorities overseas but indicating that Japan acted alone.

Noda declined to comment on whether the intervention, thefirst since March 2004, was to buy dollars for yen, but twotraders said the Bank of Japan appeared to have bought dollarsaround 83 yen.

"We will take decisive steps if necessary, includingintervention, while continuing to closely watch currency marketmoves from now on," Noda told reporters at a hastily arrangednews conference.

The dollar, which had hit a 15-year-low at 82.87 yen earlierin the day, spiked one yen higher and was trading up 1.6 percenton the day at 84.50 yen.

Prime Minister Naoto Kan's government has been trying to talkdown the yen but until Wednesday had stopped short of interveningin the markets, apparently worried that acting without Group ofSeven partners would not be very effective.

Kan was re-elected ruling party leader on Tuesday, decisivelyfending off a challenge from powerbroker Ichiro Ozawa, anoutspoken advocate of intervention.

15-YEAR HIGH

"There were views in the market that Kan was more tolerant ofa higher yen and the yen rose after he won the ruling partyleadership vote yesterday," said Yasuo Yamamoto, senior economistat Mizuho Research Institute.

"The government probably wanted to stamp out those views. Butthe question is: Will the yen stop rising from here? It's notclear."

Japan has not intervened in the foreign exchange market sinceMarch 2004 after a 15-month, 35 trillion yen ($421.7 billion)selling spree aimed at preventing a strong yen from snuffing outan economic recovery.

But the yen has surged to its highest against the dollarsince 1995, as low U.S. interest rates have made the dollar cheapto borrow and sell for higher-yielding assets, bringing theJapanese currency closer and closer to its record peak of 79.75per dollar set in 1995.

The yen's rise has weighed on the Tokyo stock market's Nikkeiaverage, which climbed 1.8 percent on the day as news of theintervention spread.

The euro rose 1.5 percent to 109.65 yen.

The Bank of Japan acts on behalf of the Ministry of Financein currency intervention.

Japan is not the only developed economy to have intervened toweaken its currency in the past year.

The Swiss National Bank intervened to hold the Swiss francdown against the euro, in a move launched in March 2009 as partof a package of steps to fight deflation risks. ($1=83.00 Yen) (Reporting by Tokyo newsroom; Writing by Charlotte Cooper andLinda Sieg; Editing by Edmund Klamann)