The first incident was around 5:15 Wednesday afternoon at Brooklyn Avenue and Kingston Avenue in Crown Heights.
Police say a man in his 20s picked up a 10-year-old girl. She reportedly screamed, and the suspect threw her to the ground and fled.
A few minutes later, at Maple and Kingston, the same man allegedly grabbed a 13-year-old by her arm.
Police say she broke away and the man ran off.