An estimated 25 to 27 per cent of 1.84 crore voters exercised their franchise till midday on Thursday in the fourth phase of polling in Uttar Pradesh.

Polling is on for 53 assembly constituencies spread over 12 districts, including the backward Bundelkhand region.

The pace of voting was initially slow but picked up gradually as the day advanced, the office of UP Chief Electoral Officer said here.

Around 25 to 27 per cent polling was recorded till noon, the CEO office said, adding the exercise was by and large peaceful amid tight security arrangements.

Inter district and inter state borders have been sealed and patrolling by security forces has been intensified in poll-bound areas. Most of the sensitive polling centres are being manned by the personnel of Central Paramilitary Forces.

680 candidates are in the fray in this phase, prominent among them being sitting MLA from Rampur Khas (Pratapgarh) Aradhana Mishra who is the daughter of Congress MP Pramod Tiwari, and Independent MLA and minister Raghuraj Pratap Singh alias Raja Bhaiya, who is again contesting from his traditional Kunda (Pratapgarh) seat.

In Rae Bareli, Aditi Singh is contesting on a Congress ticket, BSP turncoat Swami Prasad Maurya's son Utkarsh Maurya is in fray from Unchahar seat, while Leader of Opposition Gaya Charan Dinkar is contesting from Naraini (Banda) seat. Senior SP leader Reoti Raman Singh's son Ujjwal Raman Singh is in the race from Karchana (Allahabad) seat.

Assembly segments in Congress President Sonia Gandhi's Rae Bareli Lok Sabha constituency are among the seats where the electoral exercise is taking place. In a first since 1998, Gandhi gave campaigning a miss in her constituency.

Other districts where polling is going on in this phase amid tight security are Pratapgarh, Kaushambi, Allahabad, Jalaun, Jhansi, Lalitpur, Mahoba, Banda, Hamirpur, Chitrakoot and Fatehpur.

The maximum number of candidates (26) are in Allahabad North, while only six candidates are in fray in Khaga (Fatehpur), Manjhanpur (Kaushambi) and Kunda (Pratapgarh).

BSP has fielded its nominees in all seats, while BJP's nominees are in 48 constituencies. BJP has left 6 seats for its ally Apna Dal. SP nominees are in contest in 30 segments and its ally Congress is in contest from 25 constituencies.

In 2012 polls, out of the 53 seats in this phase, Samajwadi Party had won 24, BJP 5, Bahujan Samaj Party 15, Congress 6 and others had got 3.

Elections for UP Legislative Assembly are being held in seven phases, with three more on February 27, March 4 and 8 to follow after today's polling. Results will be out on March 11.