The BBC's Mike Wooldridge: The Prime Minister observed a day long fast to promote religious harmony

Mr Vajpayee said the government would be unrelenting in punishing those who carried out such attacks.

Meanwhile the Minister for Tourism and Parliamentary Affairs, Madan Lal Khurana, resigned in protest at the actions of hardline allies of the ruling BJP party.

Mr Khurana, who like Mr Vajpayee comes from the moderate wing of the Hindu nationalist BJP, told a news conference in Delhi that hardline Hindu groups were actually taking steps to defame the BJP.

The BBC's Daniel Lak in Delhi: A split or moderate figthback against hardliners

The BBC India Correspondent, Daniel Lak, says Mr Khurana was already in trouble with his party for refusing to stay silent about the attacks on Christians by Hindu extremist groups and threats to disrupt the current Pakistani cricket tour of India.

Fasting for atonement

Mr Vajpayee's address was made on the 51st anniversary of the assassination of Mahatma Gandhi. He said the anniversay this year was being marked against an unhappy backdrop of sectarian violence.

Correspondents say it was the prime minister's strongest comment to date on the issue of anti-Christian and inter-caste violence.

Madan Lal Khurana is a close friend of Mr Vajpayee

Mr Vajpayee's underlined his call for tolerance with a Gandhian tactic, a protest fast on Saturday.

He said his fast would be undertaken in a spirit of "atonement and introspection".

He cited incidents ranging from the rape of nuns in Madhya Pradesh to an Australian missionary and his two young sons being burnt to death in Orissa last weekend and a massacre of 22 villagers in Bihar during the week.

"We cannot but grieve," he said. "Such incidents violated India's tradition and culture of tolerance and went against everything Gandhi stood for."

Mr Vajpayee said the laws guaranteeing protection irrespective of faith, caste and gender would be enforced without exception and to the fullest degree.

Critics not impressed

Hundreds of supporters have demonstrated their support for Mr Vajpayee's fast by gathering outside his residence.

But editorial writers and opponents of the government have been sceptical of the gesture.

The Times of India called the fast a farce. "A genuinely stricken prime minister would simply resign from office, owning responsibility for all that has happened in recent months to tarnish the country's image," it said.

Two days ago the government ordered a judicial inquiry into the killing of the missionary and his sons, allegedly by Hindu extremists.