The filing of nominations for these constituencies started at 11 am, immediately after the notification, the Chief Electoral Officer (CEO) office here said.
The last date of filing nominations is January 24 while candidature can be withdrawn till January 27. The polling will be held on February 11.
Uttar Pradesh goes to polls in seven phases between February 11 and March 8.
The first phase will cover western UP districts, including riot-scarred Muzaffarnagar and Shamli, where BJP had fared well in the 2014 Lok Sabha polls.
The other districts going to polls in the first phase are Baghpat, Meerut, Ghaziabad, Gautam Buddha Nagar, Hapur, Bulandshahr, Aligarh, Mathura, Hathras, Agra, Firozabad, Etah and Kasganj.
The Muslim-dominated areas will also be an acid test for BSP chief Mayawati, who is banking heavily on the Dalit-Muslim vote bank in the region which was once its favourite hunting ground.
This time, BSP is relying on Muslim support by giving them 97 tickets (out of 403). The poll outcome will reflect the extent to which Mayawati has been able to keep her Dalit support base intact amid intense wooing by BJP and also to what extent she can garner more Muslim support than last time.
The Samajwadi Party, now headed by Akhilesh Yadav after the EC decision in his favour, will also face a stern test in this region.
Over 2.57 crore voters, including around 1.17 crore women, will exercise their franchise in this phase.
Of these voters, 24.25 lakh are between the age group of 18 to 19 years, the CEO office said.
The turnout of voters, especially minorities, in the first two phases could give an inkling of the mood of Muslims and determine the shape of the contest.
The first phase in Muslim-dominated region could also bring out the impact of All India Majlis-e-Ittehadul Muslimeen (AIMIM) led by Asaduddin Owaisi.