SRINAGAR, August 11, 2008 (AFP) - Indian troops on Monday shot dead a prominent Kashmiri separatist leader and three other protesters as they tried to halt huge Muslim demonstrations in the revolt-hit region, witnesses said.

Sheikh Abdul Aziz, a former militant turned moderate political leader, was killed while taking part in a protest march close to the Line of Control, which separates the Indian and Pakistani parts of the Himalayan region.

A police official said three other protesters were killed in a day of fierce clashes in the disputed Kashmir valley. A doctor at Srinagar's main hospital, Manzoor Ahmed, confirmed Aziz died of a gunshot wound.

'We will spill blood for blood,' Aziz's supporters chanted as they carried his body out of the hospital.

Security forces immediately imposed a strict curfew in Srinagar, the main city in Indian Kashmir and the hub of the 19-year-old revolt against New Delhi's control over the Muslim-majority region.

Aziz, who was 52, was a prominent member of the All Parties Hurriyat Conference, an alliance of moderate Kashmiri separatist groups at the forefront of the political struggle against Indian rule over part of Kashmir.

The shooting came as Indian security forces tried to prevent about 100,000 Muslims from marching towards the de facto border with Pakistan -- one of the biggest protests ever seen in Kashmir.

The marchers had reached a point just 40 kilometres (24 miles) from the Line of Control, despite repeated efforts by Indian police and paramilitary forces to break up the demonstration with tear gas, rubber bullets and warning shots.

Police said the day's violence had also left at least 200 people injured.

Kashmiri separatist leaders had called the march to protest against an economic blockade of the Muslim-majority Kashmir valley by Hindu extremists in the south of Jammu and Kashmir state.

Muslim separatists have threatened to cross the heavily militarised Line of Control to highlight what they say is the Kashmir valley's proximity to Pakistan rather than the rest of India.

The latest tensions stem from an order by the government of India's Jammu and Kashmir state in June to donate land to a Hindu pilgrimage trust.

The decision sparked a series of violent protests by Muslims that left at least six people dead.

The plan was then cancelled, only to cause riots in Hindu-dominated Jammu, while Hindu hardliners began blocking road access to the Kashmir valley -- a move that has badly hit Muslim traders.

The blockade has led to shortages of essentials such as medicines.

Fruit growers and traders had also vowed to cross the Line of Control so they can sell their produce in Muzaffarabad, the capital of Pakistani Kashmir.

Aziz, who had been jailed on several occasions for demanding Indian Kashmir be handed to arch-rival Pakistan, is the third prominent separatist leader to have been killed since the eruption of the Muslim insurgency in 1989.

Mirwaiz Molvi Mohammed Farooq, who was chief cleric at Kashmir's main mosque, was killed by unidentified gunmen in 1990. Another top separatist, Abdul Gani Lone, was gunned down in 2002.

Militants and Indian security forces traded blame for each of those killings, which were followed by a sharp upsurge in violence.