A man has been arrested after allegedly throwing his semen over a string of women in supermarkets.

Manuel Banuelos-Alcala, 47, is accused of following strangers into shops and lobbing semen at them before walking away.

He is said to have targeted the same woman twice at a Safeway store in Portland, Oregon, as well as other victims in the same city and another in Milwaukee.

One of the alleged victims told local TV station Katu she had semen thrown at the November and again in April this year.

(Portland Police Department)

"I felt something kind of hit me in the back," she said. "Ever since it happened the first time, you're always on high alert that something's going to happen, but I did not expect it a second time."

It is not clear where he deliberately targeted the same women twice or whether it was a coincidence.

Banuelos-Alcala was arrested at the car park of the same Safeway, in the Beaverton area of the city.

Police said before his arrest he "likely committed another lewd act of throwing semen on an unsuspecting female customer".