(Cover) - EN Showbiz - Sean Penn "clutched his chest" while watching his ex-wife Madonna's racy concert.

Madonna performed at the Staples Center in Los Angeles Thursday night and Sean was front row and centre.

The 52-year-old actor and the 54-year-old singer were married from 1985 to 1989 and experienced a tumultuous union.

The pair were deeply in love even though their marriage didn't work out and Sean apparently couldn't get enough of watching his former flame onstage.

"He was practically panting," witness told Radar Online.

"Every time she thrusted or bent over, he was like Oh, man! I can't take this! She is too hot!'

"At one point she stared Sean dead in the face, smiled, unzipped her pants, and mooned the crowd, but it was really like she was mooning Sean! He laughed and clutched his chest like he was going to pass out. She was wearing a black lacey thong, and her butt looked perfect! So smooth and tight like a 20-year-old's!"

After the show, Sean was absolutely effusive.

Many thought he looked like a young man with an intense crush.

"Sean was like a teenage boy meeting his idol. [He was] gushing," another source detailed.

"It was amusing, and kind of cute.

"And it didn't end there! Sean was later witnessed going into Madonna's trailer for what we can only assume was a very special catch up!" (C) Cover Media