Sept 30 (Reuters) - U.S. office vacancy rate remained flat for the third consecutive quarter at 16.8 percent, real estate research firm Reis Inc said in a report released on Tuesday.

The recent acceleration in the labor market recovery has not yet produced meaningful vacancy compression, Reis said.

"Net absorption of 7.15 million square feet was a significant rebound from last quarter's 3.17 million square feet and is far more reflective of a market that is in the midst of a recovery," Ryan Severino, senior economist and associate director of research at Reis, said.

The outlook for the end of 2014 "remains optimistic".

The rate of average monthly job gains is strong enough to start pushing office vacancy rates down, the report said.

Nearly 4.79 million square feet of new office space came into the market in the third quarter, the lowest since the first quarter of 2013, Reis said.

Rent growth was a marginal 0.4 percent in the third quarter and registered a slight deceleration from the second quarter.

Rent growth continued to be driven by areas with significant technology or energy presence, Reis said.

Markets such as San Francisco, Dallas, San Jose, Seattle, and New York had the strongest rent growth in the quarter, Reis said.

Washington, D.C. remained the tightest office market in the United States, reporting the lowest vacancy rate of 9.4 percent, with New York following at 9.9 percent.

(Reporting by Rohit T. K. in Bangalore; Editing by Don Sebastian)