Baltimore's office vacancy rate rose slightly during the second quarter, to 17.1 percent, and rental rates for class A buildings, or newer offices with amenities, averaged $28.11 per square foot, commercial real estate company Cushman & Wakefield reported Tuesday.

Outside the city, in Anne Arundel, Harford and Howard counties, office vacancy rates have declined from the beginning of the year, helped by an increase in jobs in the area related to federal base restructuring, the report said. The Baltimore region, including the city and Baltimore, Anne Arundel, Howard and Harford counties, had a vacancy rate of 13.4 percent, the report said.

Baltimore City's vacancy rate bumped up less than a percentage point in part because of the June opening of the 277,000-square-foot Thames Street Wharf building between the Inner Harbor and Fells Point, where Morgan Stanley occupies just over half the space.

Most new leases were signed in the city's business district or around Baltimore-Washington International Thurgood Marshall Airport or the I-83 corridor in Baltimore County. About 1.2 million square feet worth of new office space is under construction, mostly outside of Baltimore's business district, of which about 900,000 should be completed this year, Cushman & Wakefield said.

—Lorraine Mirabella