NEW YORK - New York City Mayor Bill De Blasio on Monday expressed sorrow for the two slain police officers, calling on Americans to respect and support the police.

"Show great respect for these two families, show respect and support for our police," the mayor said during a press conference.

"We as citizens have an obligation to join in protecting our police just as they protect us," he added.

Two New York police officers were shot dead in an ambush Saturday afternoon, which investigators believe was a revenge for Eric Garner and Michael Brown, two African-Americans who were killed separately by police.

Ismaaiyl Brinsley, the 28-year-old gunman, killed himself with a shot to the head at a nearby subway station, soon after he shot dead the police officers.

The mayor urged Americans to see this attack as an attack not only on US citizens, but also an attack on all police.

"There is sometimes a proclivity, a cynicism in our society, there is less faith than there once was, or should be, today in our institutions and our leaders," he pointed out.

"Well I say equally, if anyone of bad intent threatens a police officer - on the Internet or anywhere else - anyone who hears such a threat must deliver that information immediately to the NYPD, must turn that individual in," he said.

"It is all of our obligation, to take the information we have and use it, and ensure there aren't future tragedies," he added.

The killings of unarmed Garner and Brown by police have triggered persistent protests within and even out of the United States.