Crowds gathered outside the Mumbai hospital

Doctors treating Mr Mahajan, a former federal minister, said he succumbed to bullet injuries at 1610 (1040 GMT).

His brother, Praveen, is charged with attempted murder and is in being held in police custody.

Senior BJP leaders have gathered outside Mumbai's Hinduja hospital where Mahajan was being treated.

It is unfortunate that the country has lost a young leader with a lot of promise Manmohan Singh Indian prime minister Obituary: Pramod Mahajan

Others have gathered at the party headquarters in Delhi where the party flag has been lowered.

Indian Prime Minister Manmohan Singh led the condolences and said it was unfortunate India had lost a young leader with a lot of promise.

"A charismatic and youthful leader, Pramod Mahajan was full of promise and energy. It is indeed tragic that he has been snatched away from us at the prime of his career," he said.

Former Prime Minister Atal Behari Vajpayee said: "His personality, hard work and his ability to take everybody along not only benefited the party but proved equally beneficial for the country's development," he said.

Praveen Mahajan is in police custody

Reports say Mr Mahajan's brother fired at him from close range in the Mr Mahahan's Mumbai apartment because of a family dispute.

Three shots were allegedly fired by Praveen Mahajan from his licensed revolver.

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The BBC's Zubair Ahmed in Mumbai says Mr Mahajan, 56, was one of the most recognised political figures in India.

Although he lacked a political base, he was an influential figure in the BJP where he was part of the party's Generation Next - a group of savvy and relatively younger "technocrat" leaders.

Our correspondent says he played a pivotal role in modernising the party.

A former telecommunications minister, he is credited with bringing about a telecommunication revolution in the country.