The announcement was made late tonight by Shahi Imam of Fatehpuri mosque Maulana Mufti Mukkaram Ahmed, reversing an earlier announcement which had said that it will start from Sunday.
"The sky was cloudy and we could not sight the new moon, so we had earlier decided that the month of Ramzan will begin from Sunday.
"However, we later contacted Maulanas in various parts of the country like Hyderabad and Srinagar who told us that they have sighted the moon. So, we have decided to reverse the earlier decision," Mukkaram told PTI.
Ramzan, the ninth month of the Islamic lunar calendar, is observed as a fasting period by Muslims who abstain from food and water from sunrise to sunset.
The month-long fasting will culminate in the Id-ul-Fitr celebrations next month.