Mukhtar Ansari's family has alleged the imprisoned gangster-politician who died on Thursday had been given "slow poison in Banda jail", prompting a chief judicial magistrate to order a judicial probe.

Mukhtar, 63, in jail since 2005 and serving various sentences including two life terms for murder and other offences, had last week alleged a plot to murder him.

Mukhtar was a five-time MLA from Mau — twice as BSP nominee, twice as an Independent and once as a candidate of his own Qaumi Ekta Dal — and his family has deep links with the Samajwadi Party.

"We have confirmed information that my father was given poison in his daily food," Mukhtar’s youngest son Umar Ansari told reporters in Banda.

It was on an appeal from Umar that Bhagwandas Gupta, CJM of the MP/MLA court in Banda, ordered the judicial probe. Sources said additional CJM Garima Singh would conduct the inquiry and submit the report within a month.

Samajwadi president Akhilesh Yadav, however, demanded an inquiry under the supervision of a Supreme Court judge. BSP president Mayawati too sought a "high-level inquiry".

The state government banned gatherings of more than four people anywhere in Uttar Pradesh on Friday.

After the post-mortem, Mukhtar’s body was taken to his home district of Ghazipur with about 20 policemen providing security. The post-mortem report had not been made public till late Friday night.

Ghazipur superintendent of police Omvir Singh told reporters Mukhtar would be buried on Saturday.

Mukhtar had complained of chest pain and was taken to the Rani Durgavati Medical College Hospital on Thursday night. He was declared dead after initial treatment.

“He was brought unconscious and died after cardiac arrest,” medical college principal Suneel Kaushal said.

Mukhtar’s eldest brother Sigbatullah said: “We came to know from our sources that he was served with a poisoned dinner on March 19. He was admitted to hospital but the doctors didn’t treat him.”

Mukhtar had written to the CJM’s court on March 21 that a conspiracy had been hatched to kill him.

He had cited how several accused — including Prem Prakash Singh alias Munna Bajrangi — had been killed in jail. Bajrangi was allegedly shot dead by Sunil Rathi, another alleged gangster, in Baghpat jail on July 9, 2018.

Gangster-politician Atiq Ahmad and his brother Ashraf were shot dead by three gunmen at the gate of an Allahabad hospital on April 15 last year. The brothershad been brought from Naini jail for routine medical examinations.

Mukhtar’s elder brother Afzal is seeking re-election from the Ghazipur Lok Sabha seat as a Samajwadi candidate. Sibgatullah is a former Samajwadi MLA.

One of Mukhtar’s sons, Abbas Ansari, is MLA from Mau and represents the Suheldev Bharatiya Samaj Party, an ally of the ruling BJP. Mukhtar’s nephew Suhaib Ansari is Samajwadi MLA from Mohammadabad.

Mukhtar had been awarded life terms in two cases of murder and illegal arms, and sentences of 3 to 10 years in five other cases of murder, kidnapping and intimidation. This apart, 21 of the 66 cases against him were pending while he had been acquitted in the remaining 38 cases.