Residents in Greenport are on alert for a persistent peeping Tom who has been spotted lurking near windows in the village at night.

Police say at least three or four people this summer have caught sight of a man peering into their windows, mostly between the hours of 1 a.m. and 6 a.m. In some cases, police say the suspect was committing a lewd act.

"Someone awakens in the middle of the night and sees the silhouette of a man looking in the window, we've had this happen numerous times," says Southold Police Chief Martin Flatley.

In at least one case, the suspect reached through a window to peel back window treatments. "A hand actually came in the window and moved the curtains aside," Flatley says.

Kathleen Bifuolco, of Greenport, knows how unsettling it is to be watched. It happened to her several years ago.

"I was at my sink and the kitchen window's right there, and I saw movement that I know wasn't me -- and I saw what it really was," she says. "It's very frightening. You don't expect to see that and you don't expect someone to be basically invading your space and your yard, watching you."

In Bifuolco's case, a man was arrested and served time.

To track down the suspect in the most recent cases, police say they've boosted patrols in certain neighborhoods and are also using a K-9 to track down leads. But investigators say none of the victims in the recent cases got a good look at the suspect, and therefore have been unable to provide police with a definitive description.

The description that investigators have been able to glean from victims' glimpses is that of a heavyset black male who wears black clothing. But police say the victims have been unable to sufficiently pick a suspect out of a photo array.

In the meantime, authorities are urging residents to keep their windows locked and covered, and to add outdoor motion-senor lighting where possible.