TOKYO, May 31 - Japan's Ministry of Finance (MOF) sold yen for the third time in over a week on Friday in an apparent bid to prevent a surging yen from hampering an export-led recovery in the economy. As if a downgrade of its sovereign rating wasn't enough, Japan spent what market sources estimated to be billions of dollars to rein in the yen, which continued its upward charge despite the rating action. Moody's Investors Service, in a closely watched decision, delivered a bigger-than-expected two-notch cut to Japan's local currency rating on government debt to A2 from Aa3 on Friday. It changed the outlook to stable. Following yen-selling intervention last Wednesday and Thursday, the ministry bought dollars for yen as it fell to around 123.00 yen, within striking distance of a six-month low of 122.82 in New York. "We intervened because the currency movements were too rapid. We will continue to monitor the market and take appropraite action as needed," Zembei Mizoguchi, head of the ministry's international bureau, told . "We will act whenever the timing is most effective." His boss, Finance Minister Masajuro Shiokawa, issued a similar comment in a statement prepared for the intervention. The dollar initially jumped to 124.45/50 yen from 123.10/20 before the intervention, market dealers said. By 0740 GMT, the greenback had eased back to 123.96/97 yen, and analysts said intervention could continue. "I think they will have to intervene more in the future since if left untouched, the dollar would continue to slip against the yen," said Koji Fukaya, chief forex analyst at Bank of Tokyo-Mitsubishi. "They will have to continue absorbing yen demand through interventions and a fairly big amount of funds will be needed for this," he said, eyeing the MOF's pain threshold at 124 yen. It was the third time since last week that the Bank of Japan came into the market on behalf of the MOF, which has said it was acting to prevent rapid fluctuations in foreign exchange rates. Japan is seen worried about a strengthening currency dimming export competitiveness and eating away at profits at exporting companies. The latest string of interventions started on May 22 after the yen climbed to a 5-ВЅ month high of 123.50 to the dollar. It intervened again the following day, pushing the dollar up almost one full yen to around 124.80. The yen has been strong in recent days because of growing evidence that Japan has pulled out of its third recession in a decade. Economists expect growth in Japan in the first quarter could have reached an annualised rate of more than eight percent, handily outpacing the United States.