Underworld gangster Dawood Ibrahim is critical, according to media reports. (File)

Highlights Dawood Ibrahim suffers heart attack, is admitted to a hospital in Karachi

Islamabad has always denied Dawood's presence in Pakistan

Dawood Ibrahim is accused of plotting the 1993 serial blasts in Mumbai

Dawood Ibrahim, India's most-wanted, is in a critical condition at a hospital in Pakistan's Karachi, media reports say. The 61-year-old underworld don suffered a heart attack and was admitted to the Aga Khan Hospital in the city, according to unverified reports. But Dawood Ibrahim's close aide Chhota Shakeel dismissed the reports, saying he was fine.Dawood is accused of plotting the 1993 serial blasts in Mumbai in which 257 people were killed and 700 were injured. The mafia don is believed to have financed the attacks on orders from Pakistan's Inter-Services Intelligence. He is also accused of masterminding other terror attacks and faced multiple charges of money laundering and extortion. India and the US also say that Dawood financed terror groups including al Qaeda and Lashkar-e-Taiba.India has tried for many years to track down and apprehend Dawood, who is said to have run Mumbai's underworld by remote control out of Dubai and Karachi.India maintains that the underworld don has, for years, been shielded by Pakistan and has multiple addresses in Karachi, something that was endorsed by a United Nations committee, which accepted six of the nine addresses that New Delhi had submitted as his hideouts in that country last year.India has submitted several dossiers that it says are proof that Dawood lives on Clifton Road in Karachi.

Islamabad, however, has always denied Dawood's presence in Pakistan.Last year, Dawood joined his family via Skype in the celebrations of the wedding of his nephew to the daughter of a Mumbai businessman. His nephew Alishah Parkar is the son of the gangster's sister, Haseena Parkar, who died three years ago and was a senior member of his mafia.