By Bappa Majumdar

NEW DELHI, Aug 15 (Reuters) - India rolled out a security clampdown on Friday ahead of annual Independence Day celebrations following recent bomb attacks on some of its cities and violent protests in its northern region of Kashmir.

Snipers will keep a close watch from high-rise buildings as Prime Minister Manmohan Singh unfurls the national flag from the ramparts of Delhi's historic Red Fort to a 21-gun salute before addressing the nation.

But as India celebrates the 61st anniversary of independence from British colonial rule, security forces will be on alert across the country to prevent attacks from separatist militants or Maoist rebels.

"We have geared up resources and will have anti-air attack systems in place in the capital. Some areas have been declared no-fly zones," said Rajan Bhagat, a Delhi police spokesman.

In Kashmir, at least 27 people have been killed since June in some of the biggest protests since a revolt against Indian rule broke out in 1989.

The trouble began when the government promised to give forest land to a trust that runs Amarnath, a cave shrine visited by Hindu pilgrims. After huge protests by Muslims, it backtracked, in turn angering Hindus in the Jammu region of the state.

The disputed region's main separatist alliance has called a general strike for Friday.

"We appeal to people to observe August 15 as a black day and stay away from Indian functions," the All Parties Hurriyat (Freedom) Conference said in a statement.

In New Delhi, barricades have been put up on roads and police were frisking people in malls and checking bags.

On Thursday, the government sweetened the celebrations for five million of its workers, agreeing to hefty pay rises.

Singh's ruling coalition has had a tough time of late, struggling to contain inflation while being pilloried by the opposition for failing to prevent or solve a series of deadly bombings in some of the country's cities.

The attacks have killed more than a 100 people since May.

In forests in central and eastern areas, Maoist rebels are becoming increasingly assertive and have told people not to celebrate.

In the remote northeast, four powerful separatist groups, including the United Liberation Front of Asom (ULFA), have also called a boycott and a general strike.

On Thursday, security forces gunned down four ULFA rebels, but the militants have vowed to strike back.

"Militants are planning disruptive activities in a big way in the region," a senior intelligence official told Reuters. (Additional reporting by Sheikh Mushtaq in Srinagar, Biswajyoti Das in Guwahati and Sujeet Kumar in Raipur; Editing by Mark Williams)

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