The Great Gatsby, warned

I'd like to know if "warned" in the following excerpt of the chapter Seven of The Great Gatsby means "informed" or "premonished", "to have a feeling of":

That locality was always vaguely disquieting, even in the broad glare of afternoon, and now I turned my head as though I had been warned of something behind. Over the ashheaps the giant eyes of Doctor T. J. Eckleburg kept their vigil but I perceived, after a moment, that other eyes were regarding us with peculiar intensity from less than twenty feet away.

Thank you.