US existing-home sales surged in May to their strongest pace in nearly six years as more first-time buyers entered the market, the National Association of Realtors said Monday.

Sales of existing, or used, homes leaped 5.1 percent from April to an annual pace of 5.35 million units.

"Solid sales gains were seen throughout the country in May as more homeowners listed their home for sale and therefore provided greater choices for buyers," said Lawrence Yun, NAR's chief economist.

"However, overall supply still remains tight, homes are selling fast and price growth in many markets continues to teeter at or near double-digit appreciation."

Buyers snapped up single-family homes, townhouses and condominiums at the highest rate since November 2009, surpassing analysts' consensus estimate of a 5.26 million units annual pace.

Sales were up 9.2 percent over May 2014 and marked the eight straight month of year-over-year increases as the housing market appears to be benefiting from modest wage growth and a tightening labor market.

The percentage of first-time buyers rose to 32 percent in May, the highest level since September 2012. An important indicator of consumer interest in the housing market, the share of first-time buyers was only 27 percent a year ago.

"The return of first-time buyers in May is an encouraging sign," said Yun.

Supply remained tight at 2.29 million homes, though it was up 3.2 percent from April, with unsold inventory slipping a tick to a 5.1-month supply at the current sales pace.

The median existing-home price in May was $228,700, a gain of $10,000 from April. Compared with a year ago, the overall median price was up 7.9 percent; the massive single-family home market scored a price gain of 8.6 percent.

"Sales have been highly volatile in recent months but the net result appears to be a solid uptrend," said Jim O'Sullivan, chief US economist at High Frequency Economics.