"
Enough... No-one believes in you, Denktash, no-one trusts you any longer. Resign and open the way to peace
"
Union leader Ali Gulle
The march - one of the biggest in the northern Turkish part of Cyprus - follows the failure of Turkish and Greek Cypriots to reach an agreement at the EU summit in Copenhagen earlier this month.
Opposition figures have accused Mr Denktash of blocking progress on a United Nations plan to reunify Cyprus by the end of February.
The ultimate aim of the plan would see a united island join the EU in May 2004.
"Yes to the plan, yes to the EU," the crowd chanted, some of them holding olive branches, others waving blue EU flags.
"Denktash will not put his signature to peace," Ali Gulle, a union leader, told a crowd of thousands gathered in the main square in Turkish-held northern Nicosia.
"Enough... No-one believes in you, Denktash, no-one trusts you any longer. Resign and open the way to peace," Mr Gulle said.
Mr Denktash, who is recovering from two heart operations performed earlier this year, is currently in Ankara where he has been holding talks with Turkish authorities.
Greek-Cypriot political parties and the confederation of Greek-Cypriot trade unions issued statements hailing the demonstration as part of a common effort by Greek and Turkish Cypriots for the reunification of the island.
Thursday's demonstration was the latest of several organised in recent months by unions and other non-governmental organisations which want an end to the division of the island.
If the two sides fail to reach agreement on reunification by the end of February, only the Greek part of Cyprus will enter the EU.