Amazon.com, the giant online retailer with the seemingly bottomless appetite for Seattle office space, is gobbling up still more.

Vulcan Real Estate said Tuesday it has agreed to construct two buildings totaling 380,000 square feet for Amazon.

The $160 million project will be two blocks west of the company’s existing headquarters complex in South Lake Union, which Vulcan listed for sale last week.

The two linked buildings would cover most of the block bounded by Westlake Avenue North, Ninth Avenue North, Mercer and Republican streets. It’s now mostly parking lots.

Construction of the five- and six-story buildings should start in January, Vulcan said, and Amazon should move in by early 2015.

Amazon’s 365,000-square-foot lease is for 16 years. The project also would have 15,000 square feet of street-level retail space and 546 underground parking stalls.

Vulcan began seeking city permits for the buildings this spring but said it wouldn’t break ground until it had signed a tenant.

The new buildings bring Amazon’s total office-lease commitments in South Lake Union and the Denny Triangle to more than 3 million square feet. In addition to its 1.7 million-square-foot headquarters complex, it rents space at 2201 Westlake, West 8th, 1918 Eighth and 1260 Mercer.

Amazon also plans to build a 3.3 million-square-foot high-rise office complex in the Denny Triangle, on three blocks it is buying from Seattle’s Clise Properties. It has said it expects to break ground on the first tower next year.

Although Amazon’s total planned Seattle office footprint now exceeds 6 million square feet, that’s still less than half the space Microsoft owns and leases in the Puget Sound area.

Eric Pryne: epryne@seattletimes.com or 206-464-2231