"Long live liberty," the protestors on Sunday chanted in Arabic and Kurdish as the trials of three Kurdish activists got under way. "We want democracy … End the emergency laws".
The authorities dispatched 15 riot police to the courthouse, but they did not intervene.
Placards brandished by the demonstrators demanded the release of political prisoners, many of them members of Syria's 1.5 million-strong Kurdish minority.
Pictures of Kurdish cleric Shaikh Mohammed Mashuq al-Jaznawi figured prominently. The shaikh has not been seen since he left the Islamic Studies Centre in Damascus on Tuesday, said rights lawyer Anwar Bunni.
As the demonstration unfolded outside, the state security court jailed one Kurdish activist and adjourned the trials of two others.
Abdul Rahman Mahmud Ali, of the mainly Turkish-based Kurdistan Workers' Party (PKK), was sentenced to two years for "membership of an underground organisation seeking to annex Syrian territory to another country", Bunni said.
The PKK, which waged a bloody campaign for self-rule in Kurdish regions of southeastern Turkey from 1984 to 1999, once championed a state encompassing all Kurdish-inhabited territory, including northern Syria, although it has since moderated its line.
"Despite all their claims, the Syrian authorities are continuing to use the security services and this illegitimate court to repress society and political parties"
The court adjourned until 19 June the trial of another Kurdish activist - Shevan Abdo - detained more than a year ago after clashes with security forces in March 2004.
The court adjourned until next Sunday the case of Mahmud Ali Mohammad, an official in the Kurdish Al-Wahda party who was also arrested last year.
Bunni hit out at the continued use of the security court, whose verdicts cannot be appealed, for trying political activists.
"Despite all their claims, the Syrian authorities are continuing to use the security services and this illegitimate court to repress society and political parties," the rights lawyer said.
Kurdish activists say they have been hit by a fresh wave of arrests in recent weeks after the major crackdown of last year.
Bashar al-Assad has recently
freed Kurdish political prisoners
"This new wave of arrests ... flies in the face of the amnesty for 312 Kurdish prisoners announced by President (Bashar al-Assad) on March 30," the leader of the Kurdish Yakiti party, Hassen Saleh, told Al-Arabiya television on Thursday.
"Despite the amnesty, more than 100 Kurds detained in last year's crackdown remain in jail," Saleh said.
The Kurds, who make up about 9% of Syria's largely Arab population, have been campaigning for recognition of their language and respect for their civil rights.