Want to delete photos from iPhone. Not synced to iCloud but old photos cannot be deleted. Turned off syncing, transferred photos to Mac. Newer photos delete on syncing to Mac but not older photos either individually or by group.

Probably you have synced these Photos from your Mac/PC through iTunes. UN-sync then they would be gone from iPhone.

UN-Sync photos to your device

1. Connect your device to your Mac.
2. You can connect your device using a USB or USB-C cable or using a Wi-Fi connection. To turn on Wi-Fi syncing, see Sync content between your Mac and iPhone or iPad over Wi-Fi.
3. In the Finder  on your Mac, select the device in the Finder sidebar.
4. 
5. Select Photos in the button bar.
6. 
7. Note: When iCloud Photos is turned on, no photo syncing options appear when you select Photos in the button bar.
8. Select “Sync Photos to your device from” tickbox, then choose Photos, Pictures or a folder from the pop-up menu.
9. 
10. Uncheck Sync photos
11. Click on Apply / Sync