By Ayanjit Sen BBC reporter in Delhi

Mahatma Gandhi was assassinated in 1948

They are concerned over Veer Savarkar's links to Hindu nationalism.

Critics allege that Savakar was connected to the assassination of revered independence leader Mahatma Gandhi.

Opposition MPs walked out as President APJ Abdul Kalam unveiled the portrait in parliament's central hall on Thursday.

Savarkar's portrait joins a gallery which includes Gandhi himself and India's first prime minister, Jawaharlal Nehru, among others.

Gandhi's followers are aghast at the idea of Savarkar sharing the same pedestal as their hero.

Nationalism

Veer Savarkar served as president of the Hindu Mahasabha (Grand Assembly).

It was suspected of being involved in Gandhi's assassination by Hindu extremist Nathuram Godse on 31 January 1948.

Savarkar's role in the Indian freedom struggle and his advocacy of a "Hindu nation" is hotly disputed.

He is regarded as the Hindu counterpart of Mohammad Ali Jinnah - Pakistan's founder - for preaching a two-nation theory on the basis of religion which ultimately led to the formation of Pakistan and India.

Savarkar spent time in prison during British rule in India. He died in 1966 at the age of 83.

Tragedy

Opposition parties lobbied the president to reconsider his decision to attend Wednesday's ceremony.

They accuse the ruling BJP of pushing a Hindu nationalist agenda.

A senior leader of the Communist Party of India (Marxist), Somnath Chatterjee, said: "It will be a great tragedy if the central hall of parliament is utilised for installing the portrait of VD Savarkar."

But a senior BJP leader - VK Malhotra - said no political party had protested when the decision was originally taken to hang the portrait.

The decision was taken by a parliamentary committee consisting of leaders from different parties, including the opposition.