Two men were killed today in separate shootings in different parts of Philadelphia, police said.

In the latest slaying, a 36-year-old man was shot once in the back of the head at 39th Street and Haverford Avenue in West Philadelphia's Mantua section about 9:30 a.m., police said.

The victim, whose name has not been released died at 9:51 a.m. at the Hospital of the University of Pennsylvania, police said.

Police broadcast an alert for a man wearing a green hat and a dark hoodie.

Earlier, a 23-year-old man was shot once in the chest at 3:17 a.m. while sitting on a porch on the 2200 block of North Gratz Street, police said.

He was taken to Temple University Hospital, but was pronounced dead at 3:35 a.m.

No word yet on a possible motive, but witnesses told police the gunman fled on foot northbound on Gratz.