Sheikh Mashouk al-Khaznawi, a scholar and strong proponent of Kurdish rights, was visiting an Islamic study centre in Damascus when he went missing last month.
His body was found in a morgue on Wednesday and returned to his home town northeast of the capital, where Kurds converged in the street to protest his death.
"My father was subjected to a lot of harassment before his death because of his stands backing the Kurdish cause," said Mohammed al-Khaznawi, the sheikh's 30-year-old son.
Murshed al-Khaznawi, another son, called on Syrian authorities to reveal the truth concerning the cleric's death.
In Qamishli, a mainly Kurdish city 775km northeast of Damascus, many shops were closed on Thursday to show solidarity with Sheikh al-Khaznawi.
Syria's official media said on Wednesday that two men had been arrested for kidnapping and killing al-Khaznawi and denied that security agents were involved.
It added that al-Khaznawi's killing was criminal and that it was not related to any political or security issue.
But the Arab Committee for Human Rights said in a statement that the crime was more likely to be political according to investigations the committee has been carrying out.
The committee called for an independent Syrian Arab committee to interrogate government security branches that were accused of the killing.
There are 1.5 million Kurds in Syria, a nation of 18.5 million, including about 160,000 who are denied Syrian citizenship.