Someone set fire to a backpack and left it on the steps of a Brooklyn Jewish center early Wednesday — on the Yom Kippur high holy day, police said.

Officers from the 78th Precinct responded and saw the backpack burning on the front steps of the Park Slope Jewish Center around 1 a.m.

The FDNY extinguished the fire.

An unknown man was observed rummaging through the backpack and setting it on fire, police sources said.

The firebug fled on foot.

The NYPD said Tuesday it was stepping up patrols around synagogues ahead of Yom Kippur.