Long Island home sellers had their busiest first quarter in more than a decade, as rising city home prices drove buyers into the suburbs.

The year got off to a rollicking start in Nassau County and western Suffolk County, with 5,478 closed home sales in the first three months of 2016, a 28 percent jump from a year earlier, a new report by brokerage Douglas Elliman and appraisal firm Miller Samuel shows. It was the most active January-through-March period since 2003, when there were 6,833 sales in the first quarter.

Prices got only a moderate boost from all the recent activity. The median price increased by 2.8 percent year-over-year, to $370,000. The figures exclude East End sales.

Homebuyers “are looking at prices in the city and they’re kind of off the wall,” said Dottie Herman, chief executive of Manhattan-based Douglas Elliman. In much of Manhattan, she said, it’s hard to find a studio for less than $750,000. On the same budget in parts of Long Island, Herman said, “it looks like you can buy a mansion.”

Big jumps in sales — and modest price increases — are a common theme in New York City’s suburbs and throughout the country, said Jonathan Miller, chief executive of Miller Samuel, which publishes reports on 18 markets nationwide.

Sales are so brisk because high rental prices and low mortgage interest rates are motivating more people to buy, even as rising home values give current homeowners the equity they need to purchase their next place, Miller said.

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The increased equity “makes people more mobile, so there’s just more churn,” Miller said. However, tight lending conditions keep a lid on demand for homes, he said.

Suffolk’s sales increased by nearly 36 percent year-over-year, compared with a 21.4 percent annual gain in Nassau. The median price rose by 3 percent annually in Suffolk, to $312,000, and by 4.8 percent in Nassau, to $435,000.

“You get a little bit more house for the money, so I think that’s what’s attracting buyers to Suffolk County,” especially in the western communities with easier access to the city, said John Haines, a real estate agent with Daniel Gale Sotheby’s International Realty in Cold Spring Harbor.

In the Hamptons, the median sales price slipped by 2.8 percent annually, to $895,000, as the number of sales dropped by 19 percent, to 437 in the first quarter, Douglas Elliman and Miller Samuel reported.

The number of sales actually increased in the North Fork and the relatively lower-priced areas of the South Fork, such as the Town of East Hampton-Wainscott area, Sag Harbor, North Haven and Shelter Island, Manhattan-based brokerage Corcoran reported Thursday. Homes priced under $1 million are especially in demand, said Ernest Cervi, Corcoran’s executive managing director for the East End.

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“Entry-level homes are selling very quickly, and often with bidding wars,” Cervi said. “We’ve certainly seen a definite uptick since the weather has gotten nice.”