NEW YORK (AP) _ ''Hill Street Blues,'' which helped its ratings this season by having Capt. Frank Furillo shot and officer Joe Coffey murdered, will be back for a seventh season, NBC announced Thursday.

As part of the network's drive to promote the critically praised series, the renewal was being announced on the air by an NBC vice president, John Litvack, at the end of Thursday night's episode.

''Hill Street'' got its best ratings in two years on Feb. 13 when Furillo, played by Daniel J. Travanti, was shot. It scored a 19.6 rating and a 31 share, more than three points better than its season average.

The Feb. 27 episode in which Ed Marinaro's character was killed got an 18.7 rating, compared witho a season average of 16.3.

The show, produced by MTM Enterprises, has 26 Emmy Awards in its first five seasons, including two for Travanti as best lead actor in a dramatic series.