Buyers led by investors and developers spent nearly $1 billion acquiring commercial real estate in Hawaii during the first half of this year, according to a new report that suggests the activity may represent the first strong and sustainable resurgence since a decline began six years ago.

The report released today by Colliers International said $942 million in commercial property statewide — including retail centers, office buildings and development property — was sold during the six-month period.

Transaction volume had fallen for four straight years after peaking in 2005. A gain materialized in 2010 but volume slipped again last year. Volume this year through June is 111 percent higher than the $450 million in sales for the same period last year.

"Hawaii’s outlook is brightening as market dynamics are beginning to trend into positive territory," Colliers said in the report.

The report said low interest rates and efforts by lenders to expand loan volumes should help facilitate growth this year in Hawaii commercial real estate sales.

Colliers forecasts that sales for the full year should near $2 billion, which would eclipse the $1.2 billion last year and the $1.5 billion the year before. Still, it would be well below the $3 billion to $4 billion in annual transaction volume from 2004 to 2007 during the most recent market boom.

The big boost so far this year was led by two major sales involving pieces of Hawaii’s two largest shopping centers, Ala Moana Center and Pearlridge Center.

In May an affiliate of Ohio-based Glimcher Realty Trust that owned a 20 percent stake in Pearlridge bought the balance from a New York investment fund for $289 million. That deal included all of the mall except for a wing once occupied by J.C. Penney that is owned by a local investment firm.

The other dominant deal was the $250 million purchase of the Sears store at Ala Moana by the mall’s owner, General Growth Properties, which plans to redevelop the site and enlarge the mall’s footprint.

One very big real estate transaction not included in the report was the sale of Lanai. Developer Castle & Cooke Inc. sold 98 percent of the island it owned to Larry Ellison, the co-founder and CEO of software firm Oracle Corp., in June.

The deal included two Four Seasons resort hotels with adjacent golf courses and roughly 88,000 acres of land valued by Maui County for property tax purposes at $325 million. But Castle & Cooke structured the deal as a sale of a business, Castle & Cooke Resorts, as opposed to a real estate sale. So the sale price is not publicly known and wasn’t included in the Colliers report.

Colliers counts sales of commercial real estate over $1 million in its report.

Hawaii-based buyers did most of the purchasing — about 60 of 77 transactions this year through June. But mainland and international buyers did the bigger deals, with an average purchase of $46.3 million compared with $2.6 million for Hawaii buyers.

The 77 sales at midyear was down from 88 a year earlier. But the average price was $12.7 million compared with $5.1 million in the same comparable period.

It remains to be seen whether enough big sales or a lot of smaller sales will happen in the second half of this year to produce the overall gain Colliers expects.

Early last year Colliers projected commercial property sales would reach close to $2 billion, but they only reached $1.2 billion.

Colliers said it expects sales of distressed hotels and several multifamily housing portfolios will contribute to sales in the year’s second half to bolster full-year transaction volume.

During the first half of the year, retail properties dominated the transaction volume, representing $695 million in sales. Besides the Pearlridge and Ala Moana deals, retail sales included a neighborhood retail center in Kapa­hulu anchored by Safeway that sold for $72 million.

Office building sales totaled $96 million in the quarter, led by the $72 million sale of First Insurance Center.

Vacant commercial land sales totaled $63 million and included the sale of 160 acres of agricultural-zoned land near Maui’s Makena Golf Course, and a 1.3-acre site in Waikiki slated for development of a condominium-hotel tower.

There also were hotel sales, including the Waikiki Seaside Hotel and Days Inn on Maui.

A notable golf course, Makaha Valley Country Club, also known as Makaha East, also sold. It was bought by a company with ties to China and Canada in March for $6.4 million, according to property rec­ords.