In Google WEBMASTERS, Unfortunately i fetched few URL's which i don't want to index! after that i placed same URL in "Remove URLs" section even though those URL's still persist in "Fetch as Google" section and my question is how to remove those URL's else Google will automatically remove it? if yes when it will remove?
I'm not 100% certain on this, but I think those URLs listed in your Fetch As Google merely show historically the URLs that you have fetched in the past. But that does not necessarily mean they will stay in the index if you do a Remove URL.
If its not removed already you can use robots.txt on tour root directory using "Disalow" for the URL you want to remove. You may use regex to match more than one URL. Googlebot respects robots.txt instructions.