eerie adj.  strange in a frightening and mysterious way 
In bed at night she heard the eerie noise of the wind howling through the trees.
He had the eerie feeling that he had met this stranger before.

eerily adv. 
Her voice was eerily similar to her dead grandmother's.

eeriness noun [U] 

This page is cited from Cambridge Dictionaries Online. For the original, please visit
http://dictionary.cambridge.org/define.asp?key=eerie*1+0