Vivmark Residential will be required to sell two properties in downtown Boston to resolve some competition concerns involved in the merger that formed the company, according to the office of Massachusetts Attorney General Andrea Joy Campbell.

The required divestitures aim to ensure the combination of Equity Residential and AvalonBay Communities won't substantially reduce competition in the mid-rise and high-rise multifamily rental housing market in downtown Boston, Campbell's office said Tuesday.

The agreement resolves a preliminary investigation by Campbell's office into the deal, which closed this week. The combined company was renamed Vivmark Residential.

The agreement requires the divestiture of two buildings: 1 Emerson Place and 10 Emerson Place. The predecessor companies have also agreed to make a $500,000 contribution to support affordable-housing preservation and development in Quincy, Mass., where they collectively own and operate six apartment buildings, Campbell's office said.

Campbell's office said its preliminary investigation identified concerns that the companies' merger could substantially hurt competition, raising the risk of higher prices in a market that already has some of the highest rents in the country.

Vivmark Residential didn't immediately respond to requests for comment.