Strong rent growth has made New York City office properties some of the most valuable commercial real estate in the country. Shares of landlords focused on the city have run up in price this year, but one research firm thinks the shares still have room to grow. Bank of America raised its price targets for all New York City office REITs under its coverage by an average 5% in a research note Tuesday morning. The analysts said the city's rent growth justifies the premium asset values placed on well-located properties in the city. In particular, Midtown office vacancy is at just 5.4%, which is leading buyers of properties to underwrite 25% market rent growth over the next three years, which is more than the market forecasts of 14% growth, Bank of America says. The analysts upped their price targets on major office owners in the city: SL Green ( SLG) (up $8 to $118), Boston Properties ( BXP) (up $2 to $96), Reckson ( RA) (up $1 to $45), Equity Office ( EOP) (up $3 to $36) and Brookfield ( BPO) (up $1 to $32). The positive New York city office story has been in play for some time, and stocks focused on the region have been soaring. SL Green -- whose portfolio is centered solely on Manhattan, with several key Midtown sites -- has seen its shares run up 45% this year. Boston Properties is up 25%. SL Green rose $1.21 to $110.81 in early trading Tuesday, while Boston Properties rose 17 cents to $91.85.