Uttar Pradesh police on Monday gunned down one of the accused in the sensational February 24 killing of a prime witness in the 2005 murder case of then BSP MLA Raju Pal in an encounter here, an official said.

Police claimed that they retaliated when he opened fire at them.

Deputy Commissioner of Police Navendu Kumar told PTI that Arbaaz, who was the driver of the white SUV used by the assailants to attack witness Umesh Pal, was surrounded by police teams following an intelligence input.

He opened fire on the police and was injured in the ensuing encounter in Nehru Park under Dhoomanganj police station at around 3 pm, Kumar said.

He was taken to hospital where doctors declared him dead, the officer said.

"Arbaaz was accompanied by two or three other people who managed to escape from the spot. We are trying to track them," the officer added.

Umesh Pal and his police security guard Sandeep Nishad were shot dead on Friday outside his home in Dhoomanganj area of Prayagraj. Another security personnel Raghvendra Singh, who was injured in the attack, was admitted to SRN Hospital in critical condition and was referred to Lucknow on Sunday.

On the basis of a complaint lodged by Umesh Pal's wife Jaya Pal, a case was registered at Dhoomanganj police station (in Prayagraj) against gangster-turned politiciam Atiq Ahmed, his brother Ashraf, wife Shaista Parveen, two sons, aides Guddu Muslim and Gulam and nine others.

They have been booked under sections 147 (rioting), 148 (rioting, armed with deadly weapon), 149 (unlawful assembly), 302 (murder), 307 (attempt to murder), 506 (criminal intimidation) and 120B (criminal conspiracy) of the Indian Penal Code and provisions of the Explosive Substances Act and the Criminal Law Amendment Act, police said.

Chief Minister Yogi Adityanath had vowed to destroy the mafias after the opposition Samajwadi Party had questioned the law and order situation in the state in the wake of the killing.