By the BBC's Louise Tillin

Communal violence has been a recurring problem since India gained independence

This is not the first time that Ahmedabad, Gujarat's biggest city, has suffered communal tensions.

It was hit by violence which followed the destruction of the Babri Mosque at Ayodhya in Uttar Pradesh by Hindu hardliners in 1992 and the spill over from the ensuing intense rioting in Bombay in January 1993.

Ahmedabad was also the scene of riots between Hindus and Muslims in 1969 which led to the deaths of at least 1,000 people.

At the time there was a dispute over the leadership of the Congress Party between Indira Gandhi and Morarji Desai.

There were suggestions that violence was deliberately engineered to discredit the chief minister of Gujarat who was a supporter of Mr Desai.

Caste quotas

In 1985 and 1986 rioting erupted again in the city.

It started in protest at the Gujarat government's decision to introduce protected job quotas for the lower castes, but spiralled into violence between Hindus and Muslims.

A Muslim prays outside a burned out mosque

Communal violence in one state has often spread elsewhere in India.

The first major riots between Hindus and Muslims after the bloodshed of partition in 1947 occurred in Jabalpur in the central Indian state of Madhya Pradesh in 1961.

They were followed by riots in the northern state of Uttar Pradesh with periodic violence erupting elsewhere.

Thousands of Sikhs were murdered in Delhi in 1984.

Then the trigger was the assassination of Prime Minister Indira Gandhi at the hands of two Sikh bodyguards following her orchestration of an attack on the Golden Temple in Amritsar.

It was in the late 1980s that the roots of the current violence can be found.

The campaign which led ultimately to the destruction of the Babri Mosque at Ayodhya in 1992 was the cause of much communal rioting.

The seriousness with which the situation in Gujarat is being viewed in Delhi is a sign of how quickly such violence can spiral out of control

Following the destruction, some 2000 people were killed in communal riots in Ayodhya, Bombay and beyond.

Hindu hardline parties, including the Vishwa Hindu Prashad (VHP) and Bharatiya Janata Party (BJP) - used Ayodhya as a rallying call to Hindus throughout India.

They said the 16th century mosque at the site was located on the birthplace of the Hindu Lord Rama and that a temple had to be built there.

Nationalism arrives

This was a time of political upheaval.

The Congress Party, which had been the dominant political force since Indian independence, was on the wane.

Hindu nationalism had arrived on the political scene as an increasingly important force.

But communal politics have been around much longer.

The seriousness with which the situation in Gujarat is being viewed in Delhi is a sign of how quickly such violence can spiral out of control.