The median home price in Nassau County jumped nearly 10 percent last month compared to a year ago, as limited supply continued to drive prices up.

The median price in Nassau was $525,000 in July, 9.8 percent higher than a year earlier, the Multiple Listing Service of Long Island reported Tuesday.

In Suffolk County, the median price was $365,000, a 5.8 percent annual gain.

Nassau prices are being pushed higher by tight supply, said Kimberly Bancroft, a selling agent with Daniel Gale Sotheby’s International Realty in Locust Valley.

Bancroft, who primarily works with home buyers shopping in the $2 million to $3 million range, said “lower-priced homes here are seeing bidding wars.” Homes in the $300,000 to $800,000 range are “flying out the door,” she said.

In the higher-end housing market, sellers are being advised to “price very tightly and intelligently,” Bancroft said. “Because there are fewer buyers in that market we have to be very competitive and price well.”

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In Suffolk, Deborah Galligan, broker/owner of Marylou Swan Realty Corp. in East Patchogue, said competition has been so fierce that a recent listing for a $450,000 home received four bids over the asking price in two days.

“We haven’t had that since the heyday,” she said.

The nation’s low interest rates remain a major factor in the market, said Jerry O’Neill, broker/owner of Coldwell Banker Harbor Light in Amity Harbor.

“The fact that the interest rates continue to stay low in spite of the threat of increases, [means] buyers are coming to the market while the rates are still low,” O’Neill said.

Nassau’s median price in July was well above the record $502,500 reached in 2007, before the recession. In Suffolk, the median has yet to reach its pre-recession high of $420,000.

MLS reported last month that the median home price in Nassau reached $505,000 in June, passing the 2007 pre-recession high. But the latest MLS data revised the median price in June to $500,000.