A man died in a Brooklyn blaze early yesterday after accidentally lighting his mattress on fire, police sources said.

It began when the 39-year-old was smoking in bed at a second-floor Midwood residence on Ocean Avenue near Avenue I, the sources said.

Sixty firefighters rushed to the scene, extinguishing the flames shortly before 1:15 a.m., according to an FDNY spokesman.

The man died at Kings County Hospital after EMS rushed him there in critical condition.