Police said a 22-year-old woman met Demir at the concert late Saturday and asked to use his cellphone. Demir told the woman she could use his house phone because he lived nearby, police said. When the woman entered Demir's house, he assaulted her, police said.
The woman ran out and called 911. Police said Demir was arrested at his home.
In the other alleged attack, a 24-year-old woman was sexually assaulted about 6:30 p.m. Saturday when she got into a car near 22d and Spring Garden Streets that she mistook for a taxi. There was a man in the backseat who sexually assaulted her while another man drove, police said.
The man in the backseat forced the woman out of the vehicle at 10th and Catharine Streets after assaulting her and robbing her of $41, police said. The victim called police from there, in the Bella Vista section of South Philadelphia.
Both men were described as teenagers or in their early 20s, police said.
Contact Sulaiman Abdur-Rahman at 215-854-4851, SAbdur-Rahman@phillynews.com, or follow on Twitter @sabdurr.