Under a grey sky, men and women of all ages marched through the Kurdish-majority city waving yellow flags bearing a picture of Ocalan.

Donning puffer jackets and coats, they flashed victory signs as onlookers watched from their balconies.

Labelled the "nemesis" of the Turkish state, Ocalan remains a revered figure for Kurds not just in Turkey but across the region, despite being cut off from the outside world.

Ocalan is the only detainee at Turkey's prison island of Imrali, nearly 60 kilometres (35 miles) southwest of Istanbul.

"They put our leader in prison for no reason, and no country raised its voice against it," said Turkiya, a 60-year-old Kurdish protester in Qamishli.

Ocalan is one of the founders of the outlawed Kurdistan Workers' Party (PKK), which has waged a bloody insurgency against the Turkish state since 1984.

He was caught in Kenya outside the Greek embassy on February 15, 1999 by Turkish secret service agents after attempting to seek asylum in Europe.

The Kurdish leader was sentenced to death on charges of treason, separatism and murder that same year, but the sentence was commuted to life in prison when Turkey dropped the death penalty in 2002.

The rally aimed to show "once again that our leader has humanist ideas and that we support him", said Chahouz Hassan, who co-heads the Democratic Union Party, a Syrian offshoot of the PKK.

In the chaos of Syria's brutal eight-year war, the long-oppressed Kurdish minority has carved out a semi-autonomous region in the north of the country.

That has prompted a backlash in Ankara, which fears an entrenched Kurdish presence across the border will stoke separatist ambitions at home.

Turkey sees Syrian Kurdish fighters as "terrorists" and has repeatedly threatened to attack Kurdish-held areas along its southern border.