A woman has alerted the police after she spotted a Peeping Tom inside a ladies toilet at Reel shopping mall in downtown Jing'an District.

The woman, surnamed Zhang, said she heard sounds of clapboards when she was using the toilet on Sunday afternoon and saw a man leaning his head from one of the boards.

"I was scared and screamed immediately," Zhang said, adding that she thought it was a ghost at first. The man was wearing glasses, she said.

Zhang rushed out to chase the man, but he was gone, eastday.com reported.

She said she clearly heard the doors of each cubicle open one by one. The man probably stood on the toilet seat in the cubicle next to the one she was using.

Surveillance video showed a man wearing a black T-shirt and blue jeans wandering outside the toilet on the fourth floor around noon. After Zhang walked into the toilet, he sneaked inside.

The man did not seem to panic after being spotted by Zhang and walked out calmly, the video showed.

Police are investigating. He faces up to 10 days detention and a 500-yuan (US$80.64) fine.