Here is my recent experience. I was in London and then Istanbul in September of this year. While in London I visited the Whitechapel neighborhood which is now heavily populated with Muslims from Pakistan. There was an open air market where I took a photograph of a large booth that sold clothing. The woman who was in charge of the booth came over and asked if her image was included in the picture. When I answered in the affirmative she was adamant that I delete the picture. I did this and then scrolled though the images to show her that this was done. This spooked me about taking photographs of Muslim women even in London.
Jump forward to Istanbul. While visiting the Blue Mosque I noticed large numbers of women in traditional Muslim clothing who were taking photographs of each other and taking selfies. The prohibition about capturing the image of a woman in a photograph must vary with the different branches of Islam. There was a really cute child about 2 years old in what appeared to be a youth outfit for Islam. I requested of this child's parents permission to photograph the kid (couldn't tell if it was a boy or girl since there was so much clothing) but they said "no" which I respected.
As another person has said you can probably take photographs without permission if you have a telephoto lens are not "in someone face". Otherwise you should be respectful of a person's religion or sense of personal privacy by asking permission.
Also, don't fall for the scam of being asked for money after you have taken a photograph of someone even after you have received their permission. This happened to me in the small fishing town just below the Black Sea where the public ferry ends up on the cruise of the Bosphorus. I laughed this off and wasn't bothered anymore. I don't think these folks were scammers - they were fishermen - and probably really did not think that they could get money off me (as opposed to the "gladiators" who hang out around the Collossum in Rome.