TOKYO, Dec 6 (Reuters) - Japan's top trading firm Mitsubishi Corp plans to buy a roughly 5 percent stake in retailer Aeon for more than $325 million, and the two will work together on foreign buying amid the economic downturn, two company sources said on Saturday.

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Aeon Co, Japan's No.2 retailer, is hurt by weak consumer appetite, and hopes the move will lower the cost of buying apparel and help it better meet food safety concerns, said the sources, who asked not to be identified as they were not authorised to discuss on the talks.

Mitsubishi, which owns a 32 percent stake in convenience store chain Lawson Inc , will buy the shares on the open market for more than 30 billion yen ($326 million), becoming Aeon's top shareholder, the sources said, confirming earlier reports by the Nikkei business daily and Kyodo News Agency.

In nearly identical statements released simultaneously, the two firms said, "the contents of the reports are not factual at the moment. Should any announcement become necessary, we will announce it promptly".

Officials at both firms declined comment.

The two are likely to cooperate in making low-cost apparel in China and elsewhere in Asia and on buying safer farm produce, one source said. Mitsubishi, which invested in an Aeon distribution subsidiary in September, could also help Aeon open stores abroad, he said. (Reporting by Taiga Uranaka and Mayumi Negishi; Editing by Jan Dahinten)