whats the name of the movie...?

I'm desperatly trying to find a movie I watched as a kid. The plot is about
a bunch of teenagers who find some medallion. The medallion is needed by 3-4
disfigured people in a crypt who are trying to awake a big monster. It's
quite trashy, 80s or maybe even earlier. The scenes I remember: one of the
kids is running in the middle of the forest, police car stops by and one of
the monsters is inside. In the end they manage to awake the monster by
placing the medallion in his chest and the monster eventually destroys a
police blockade. Can't remember the title but maybe a few of the horror
experts here recognized the movie and can help me out with it...
Thanx.