Mukhtar Ansari, the 63-year-old, five-time lawmaker from the state, had been in jail in since 2005.
A gangster-turned-politician has died of cardiac arrest in the northern Indian state of Uttar Pradesh, authorities said on Thursday.
Mukhtar Ansari, the 63-year-old, five-time lawmaker from the state, had been in jail in since 2005.
Police tightened security in the state as crowds thronged outside Ansari's home after the news of his death.
Ansari, who ran his own gang in the 1990s, had more than 60 criminal cases against him, 15 of which included murder charges.
He joined politics and won his first state election in 1996 in his home constituency of Mau. He remained a lawmaker from the seat till 2022.
In April 2023, he was convicted for killing Krishnanand Rai, a lawmaker of the ruling Bharatiya Janata Party (BJP), and sentenced to 10 years in prison.
He received a life sentence earlier this month for a 1990 case involving fake arms licenses.
On Thursday, jail authorities in Banda district said Ansari was taken to hospital after he complained of vomiting.
"The patient was provided immediate medical care by a team of nine doctors," a medical bulletin by the Rani Durgavati Medical College said. "But, despite their best efforts, he died due to a cardiac arrest."
Mukhtar Ansari had been in jail since 2005.
Ansari's brother Afzal Ansari, an MP from the state, alleged that he was poisoned.
"Mukhtar said that he was given a poisonous substance in food in jail," Mr Ansari told reporters on Thursday.
"This happened for the second time. Around 40 days ago also he was given poison. And recently on 19 March and 22 March, he was again given this [poison] due to which his condition deteriorated."
Ansari had been hospitalised on Tuesday after a fall in the washroom, according to jail authorities.
He was initially treated in jail and then taken to the hospital for further treatment and discharged after 14 hours, they said in a statement.
On Thursday, following the announcement of Ansari's death, Uttar Pradesh police issued curfew orders in the state and held flag marches in certain parts.
Ansari's son Umar Ansari said he learnt the details of his father's deteriorating health through media reports and had received no information from authorities before his death.
"Two days ago, I came to meet him, but I was not allowed [to]," he said.
Ansari's post-mortem will be carried out on Friday.