This is an old movie. As far as I remember, the plot was the following:
Some guys stole/found a truck from a military convoy that turns out it had an alien inside. The alien was done by a guy in a bright green suit, kind of silly looking.
They decided to kill the alien, by cutting him in parts and burning them in the crematorium. I think, when they cut his hand and other limbs they noticed they remained moving, so it couldn’t be killed. They burnt the body.
After which, the smoke from the fire went in the atmosphere, turned into a cloud and rained down over the cemetery. Which of course lead to infecting the dead bodies and they becoming zombies.
I think the movie ended as the government nuked the town.
Saw this movie a few years back, it looked like 50s – 60s movie. It was in color. I watched it on the MGM channel, so I suspect it is MGM movie.
The movie was in English language.