NEW DELHI, Sept 3 (Reuter) - About 200 Tibetan exiles marched through the streets of the Indian capital on Wednesday in a protest against the alleged detention of an aged political prisoner in Tibet.

Clad in colourful traditional dress and carrying banners, the marchers submitted a memorandum to the Chinese Embassy with a plea to the Chinese government to release Tanak Jigme Sango from prison.

"He is the longest and oldest known political prisoner in Tibet," Tsongtsa Kalsang Topgyal of the Tibetan Centre for Human Rights and Democracy told Reuters.

"He has been there for 28 years and when he is released in 2011, he will be 85."

The Tibetan centre said Tanak, a Lhasa primary school teacher, was first arrested in 1960 on corruption charges and most recently for leading a protest at a prison.

He is one of an estimated 700 political prisoners held in Tibet, where rebellions and protests against Chinese rule have erupted periodically since the 1950s when Communist troops took control.

The Dalai Lama, Tibet's most revered spiritual leader, fled his homeland to India in 1959 after a failed uprising against Chinese rule.

In 1988 the Dalai Lama effectively tempered his calls for Tibetan independence by proposing a five-point plan for autonomy which would let China control Tibet's foreign affairs.

An estimated 130,000 Tibetan exiles live in India, with around 500 families in Delhi.

"If we continue to demonstrate and keep trying, some day they will be all released," said Ngawang Dickey, a college student taking part in the march.