American actress Kate Hudson attends "Elle Style Awards" at The Westway in London on February 12, 2008. (UPI Photo/Rune Hellestad)

LOS ANGELES, May 15 (UPI) -- U.S. film stars Kate Hudson and Owen Wilson reportedly have ended their on-again, off-again romance.

Their stormy relationship is said to have begun in September 2006.

"It was a pretty bad breakup," a friend of Wilson's told People.com. "Owen said it was a tough one. He definitely doesn't want to dwell on it. He wants to put it behind him."

The entertainment news Web site said that since they split up both have been spotted out partying in bars or clubs.

One onlooker spotted Wilson at New York's Upstairs club.

"He was pretty chummy with the ladies ... he was certainly doing some sweet talking," the spy told People.com. "He looked happy to be there hanging with them."

A source close to Hudson revealed, "She feels dumb thinking it was so serious."