A man was stabbed in the back by a woman he was arguing with Wednesday night in the South Loop.

The man, whose exact age was unknown, was arguing with a woman in a store parking lot when he tried to hit her with a broom and she stabbed him in the back with an unknown object at 9:56 p.m. in the 300 block of West Cermak, according to Chicago Police.

According to witnesses, the two had been arguing all day, police said.

The man was taken to Stroger Hospital where he was in serious condition, police said.

No one was in custody.

Area Central detectives were investigating.